SEMICONDUCTOR DEVICE WITH ELECTRICALLY FLOATING BODY

Inventor: Serguei Okhonin

RELATED APPLICATIONS

This application claims the benefit of United States (US) Patent Application number 60/897,686, filed January 26, 2007.

This application is related to LLS Patent Application number 1 1/509,188, filed by Okhonin on August 24, 2006, entitled "Memory Cell and Memory Cell Array Having an Electiically Floating Body Transistor, and Methods of Operating Same" (U.S. Patent Application Publication No. 2007/0058427).

TECHNICAL FIELD The inventions relate to a semiconductor device, architecture, memory cell, anay, and techniques for controlling and/or operating such device, cell, and array. Moie paiticularly, in one aspect, the inventions ielate to a dynamic iandom access memory ("DRAM") cell, anay, architecture and device, wherein the memory cell includes an electiically floating body configuied or operated to stoie an electrical charge.

BACKGROUND

Theie is a continuing trend to employ and/or fabricate advanced integrated circuits using techniques, mateiials and devices that impiove performance, i educe leakage curient and enhance oveiall scaling. Semiconductor-on-Insulator (SOI) is a mateiial in which such devices may be fabricated oi disposed on or in (hereinaftei collectively "on"). Such devices are blown as SOI devices and include, foi example, partially depleted (PD), fully depleted (FD) devices, multiple gate devices (foi example, double or triple gate), and Fin-FET.

One type of dynamic random access memoiy cell is based on, among other things, the electrically floating body effect of SOI transistors; see, for example, U S. Patent Number 6.969,662 (the "'662 patent) In this regard, the dynamic random access memory cell may consist of a PD oi a FD SOI transistor (or tiansistor formed in bulk material/substrate) on having a channel, which is disposed adjacent to the body and separated from the channel by a gate dielectric. The body region of the tiansistor is electrically floating in view of the insulation layer (or non-conductive region, for example, in a bulk-type material/substiate)

disposed beneath the body region The state of the memory cell is determined by the concentration of charge within the body region of the SOI transistor.

With refeience to FIGURES IA, IB and 1C, in one embodiment, semiconductor DRAM array 10 includes a plurality of memory cells 12 each including transistoi 14 having gate 16. body region 18, which is configuied to be electrically floating, source region 20 and drain region 22. The body region 18 is disposed between source region 20 and drain region 22. Moreover, body region 18 is disposed on or above region 24, which may be an insulation region (for example, in an SOI material/substrate) or non-conductive region (for example, in a bulk-type material/substrate). The insulation or non-conductive region 24 may be disposed on substrate 26

Data is written into or read from a selected memory cell by applying suitable control signals to a selected word line(s) 28, a selected source line(s) 30 and/or a selected bit line(s) 32. In response, charge carriers are accumulated in or emitted and/oi ejected from electrically floating body region 18 wherein the data states are defined by the amount of carriers within electrically floating body region 18. Notably, the entire contents of the '662 patent, including, for example, the features, attributes, architectures, configurations, materials, techniques and advantages described and illustrated therein, are incorporated by reference herein.

Refeπing to the N-channel transistor in FIGURES 2A and 2B. for example, the memory cell 12 of DRAM array 10 operates by accumulating in or emitting/ejecting majority carriers (electrons oi holes) 34 from body region 18. In this regard, conventional write techniques may accumulate majority carriers (in this example, "holes") 34 in body iegion 18 of memoiy cells 12 by, for example, impact ionization near source region 20 and/or drain region 22. (See, FIGURE 2A). The majority carriers 34 may be emitted or ejected from body region 18 by, for example, forward biasing the source/body junction and/or the drain/body junction (See, FIGURE 2B)

Notably, for at least the purposes of this discussion, logic high or logic " 1 " corresponds to, for example, an increased concentration of majority carries in the body region relative to an un-programmed device and/or a device that is programmed with logic low or logic "0". In contrast, logic low or logic "0" corresponds to, for example, a reduced concentration of majority carries in the body region relative to an un-programmed device and/or a device that is programmed with logic high or logic "1 ".

In one conventional technique, the memory cell is read by applying a small bias to the diain of the transistor as well as a gate bias which is above the threshold voltage of the

transistor. In this regard, in the context of memory cells employing N-type transistors, a positive voltage is applied to one or more word lines 28 to enable the leading of the memory cells associated with such word lines The amount of drain current is determined or affected by the charge stored in the electrically floating body region of the transistor. As such. conventional reading techniques sense the amount of the channel current provided/generated in response to the application of a predetermined voltage on the gate of the transistor of the memory cell to determine the state of the memory cell, a floating body memory cell may have two or more different current states corresponding to two or more different logical states (for example, two different current conditions/states corresponding to the two different logical states: " 1 " and "0").

In sum, conventional writing programming techniques for memory cells having an N-channel type transistor often provide an excess of majority carriers by channel impact ionization (see, FIGURE 3A) oi by band-to-band tunneling (gate-induced diain leakage ("GIDL")) (see, FIGURE 3B). The majority carrier may be removed via drain side hole removal (see, FIGURE 4A), source side hole r emoval (see. FIGURE 4B), or drain and source hole removal, for example, using the back gate pulsing (see. FIGURE 4C)

Notably, conventional programming/reading techniques often lead to relatively large power consumption (due to. for example, high writing "0" current) and relatively small memory programming window. The present inventions, in one aspect, are directed to a combination of the programming/reading methods which allows relatively low power memory programming and provides a relatively larger memory programming window (e.g . both relative to at least the conventional programming techniques) This new approach may also provide a floating body memory cell that may provide better power consumption and may include improved retention characteristics.

INCORPORATION BY REFERENCE

Each patent, patent application, and/or publication mentioned in this specification is herein incorporated by reference in its entirety to the same extent as if each individual patent, patent application, and/or publication was specifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the detailed description to follow, reference will be made to the attached drawings. These drawings show different aspects of the present inventions and.

whete appropriate, reference numerals illustrating like structures, components, materials and/or elements in different figuies are labeled similarly. It is understood that various combinations of the structures, components, materials and/or elements, other than those specifically shown, are contemplated and are within the scope of the present inventions. Moreover, theie are many inventions described and illustrated herein. The present inventions are neither limited to any single aspect noi embodiment theieof, nor to any combinations and/or permutations of such aspects and/or embodiments Moreover, each of the aspects of the present inventions, and/oi embodiments thereof, may be employed alone or in combination with one or more of the other aspects of the piesent inventions and/or embodiments thereof. For the sake of brevity, many of those permutations and combinations will not be discussed separately herein

FIGURE I A is a schematic representation of a prior art DRAM an ay including a plurality of memory cells comprised of one electrically floating body transistor;

FIGURE I B is a three-dimensional view of an exemplary prior art memory cell comprised of one electrically floating body partially depleted transistor (PD-SOI NMOS);

FIGURE 1C is a cross-sectional view of the prior ait memory cell of FIGURE IB, ci oss-sectioned along line C-C:

FIGURES 2 A and 2B aie exemplaiy schematic illustrations of the charge relationship, for a given data state, of the floating body, source and drain regions of a prior art memory cell comprised of one electrically floating body transistoi (PD-SOI NMOS);

FIGURES 3A and 3B are exemplary schematic and general illustrations of conventional methods to program a memory cell to logic state " 1 " (i e., generate oi provide an excess of majority cairier in the electrically floating body of the transistor (an N-type channel tiansistor in this exemplaiy embodiment) of the memory cell of FIGURE IB; majority carriers in these exemplary embodiments are generated oi provided by the channel electron impact ionization (FIGURE 3A) and by GIDL or band to band tunneling (FIGURE 3B);

FIGURES 4A, 4B and 4C are exemplary schematics and general illustrations of conventional methods to piogram a memory cell to logic state "0" (i.e., provide relatively fewer majority carrier by removing majority cairiers from the electrically floating body of the transistor of the memory cell of FIGURE IB; majority earners may be removed through the diain region/teiminal of the tiansistor (FIGURE 4A), the soiuce region/terminal of the transistor (FIGURE 4B), and through both drain and source regions/terminals of the

tiansistor via using the back gate pulses applied to the substrate/backside terminal of the transistor of the memoiy cell (FIGURE 4C);

FIGURE 5 illustrates an exemplary schematic (and contiol signal) of a conventional reading technique, the state of the memory cell may be determined by sensing the amount of the channel current provided/generated by the transistor of the memory cell in response to the application of a predetermined voltage on the gate of the tiansistor;

FIGURE 6 shows an electrically floating body transistor, under an embodiment;

FIGURE 7A shows electrically floating body transistor schematically illustrated as including a MOS capacitoi "component" and an intrinsic bipolar transistor "component", undei an embodiment;

FIGURE 7B is an example characteristic curve of electrically floating body transistor . under an embodiment;

FIGURES 8 A and SB show various stages of operation of tiansistor when writing or piogramming logic "1 ", under an embodiment; FIGURES 9A and 9B show various stages of operation of transistor when writing oi programming logic "0", under an embodiment;

FIGURE 10 shows an example schematic (and control signal) of an example embodiment of an aspect of the piesent inventions of holding or maintaining the data state of a memory cell when programming, foi example, a neighboring memory cell to a predetermined data state (foi example, logic state " 1 " and/or logic state "0");

FIGURE 1 1 is an example of an operation under which the data state of a memory cell may be read and/oi determined by applying control signals having piedetermined voltages to gate and source region and drain region of transistor, under an embodiment;

FIGURE 12 is a plot of voltage levels versus time foi examples of each of write "0", write "I ", and read operations, under an embodiment;

FIGURE 13 is a flow diagram for forming a transistor, under an embodiment,

FIGURE 14 shows an electrically floating body transistor in which the first portion of the body region is made discontinuous with only the diain by a third poition of the body region, under an embodiment; FIGURE 15 shows an electrically floating body transistor in which the first portion of the body region is made discontinuous with only the drain by a third poition of the body legion, under an embodiment; the source region includes a highly-doped (HD) portion and a lightly-doped (LD) poition;

FIGURE 16 shows an electrically floating body transistor in which the first portion of the body legion is made discontinuous with only the source by a second portion of the body legion, under an embodiment.

FIGURE 17 shows an electrically floating body transistor in which the first portion of the body legion is made discontinuous with the only the source by a second portion of the body region, under an embodiment; the drain region includes a highly-doped portion and a lightly-doped portion;

FIGURE 18 shows an electrically floating body transistor in which the first portion of the body legion is made discontinuous with both the souice and drain legions, and each of the source and drain regions comprise LD and/or HD portions, under an embodiment;

FIGURE 19 shows an electrically floating body transistor in which the first portion of the body legion is made discontinuous with both the source and drain regions, and each of the source and drain regions are LD. under an embodiment,

FIGLIRE 20 shows an electrically floating body transistoi in which the first portion of the body region is made discontinuous with both the source and diain regions, and the source legion is LD and the diain region is HD, under an embodiment;

FIGURE 21 shows an electrically floating body transistor in which the first portion of the body region is made discontinuous with both the source and drain regions, and the source iegion is HD and the drain region is LD. under an embodiment; FIGURE 22 shows an electrically floating body transistoi in which the fust portion of the body iegion is made discontinuous with both the source and drain regions, and each of the source and drain regions aie HD. under an embodiment;

FIGURES 23 A and 23B aie schematic block diagrams of embodiments of an integiated circuit device including, among other things, a memory cell aπay, data sense and write ciicuitry, memoiy cell selection and control circuitry, according certain aspects of the piesent inventions; and

FIGURES 24, 25 and 26 illustrate an embodiment of an exemplary memory aπay having a pluiality of memoiy cells and employing a separate souice line configuration for each row of memory cells, according to certain aspects of the ptesent inventions

DETAILED DESCRIPTION

There are many inventions described herein as well as many aspects and embodiments of those inventions. In one aspect, the present inventions are directed to a semiconductor device including an electrically floating body. In another aspect, the piesent

inventions are directed to techniques to control and/oi operate a semiconductor memory cell (and memoiy cell array having a plurality of such memoiy cells as well as an integrated circuit device including a memory cell array) having one or moie electiically floating body tiansistois in which an electrical charge is stored in the body region of the electiically floating body transistoi . The techniques of the piesent inventions may employ intrinsic bipolar transistor currents (referred to herein as "source" cunents) to contiol, write and/oi read a data state in such a memory cell. In this regard, the present inventions may employ the intrinsic source current to contiol, write and/or iead a data state in/of the electrically floating body transistor of the memory cell. The present inventions aie also directed to semiconductor memory cell, airay, ciicuitiy and device to implement such contiol and operation techniques. Notably, the memory cell and/or memory cell array may comprise a portion of an integrated circuit device, for example, logic device (such as, a microcontroller or micropiocessor) oi a portion of a memory device (such as, a discrete memory). FIGURE 6 shows an electrically floating body transistoi 14, under an embodiment.

The transistoi 14 includes a body region 18 configuied to be electrically floating. The body iegion 18 includes three portions or regions 18-1/18-2/18-3 that collectively define the electiically floating body 18. Each of the three portions 18-1/18-2/18-3 comprises the same or similai material (e.g.. P-type in this example) The transistoi 14 includes a gate 16 disposed over the first portion 18-1 of the body region 18. A gate dielectric 32 (e.g , gate oxide) is disposed between the gate 16 and the body region 18, and spaceis SP are adjacent the gate dielectric 32.

A source iegion 20 adjoins a second portion 18-2 of the body iegion 18, the second portion 18-2 of the body region is adjacent the first portion 18-1 and sepaiates the source region 20 from the fust portion 18-1 A drain region 22 adjoins a third portion 18-3 of the body region 18; the third portion 18-3 of the body region is adjacent the first portion 18-1 and separates the drain region 22 from the first portion 18-1. The source region 20 and/or diain region 22 is created using conventional doping or implantation techniques but is not so limited. The second portion 18-2 and third portion 18-3 of the body region function to electrically "disconnect" (e.g . disconnect any charge that may accumulate, disconnect any inversion channel that may form) in the first portion 18-1 from one or more of the source 20 and the drain 22 as described in detail below.

An inversion channel is generated in the body region of conventional MOSFET devices in iesponse to the application of control signals to the MOFSET. Once formed the

inveision channel provides a continuous electrical channel fiom the source region to the body region. The inversion channel of conventional devices spans the entile body region as a result of the source and drain regions being configured, relative to the gate, to each underlie the gate. In this manner, application of the appropriate gate voltage to a conventional device causes the inveision channel to form a continuous electrical channel fiom the souice to the drain region.

In contrast to conventional MOSFET devices, howevei. the souice 20 and/or diain 22 legions of an embodiment are configured so that no portion of the source 20 and/or diain 22 legions is positioned under the gate 16. Configuration of the souice 20 and/or diain 22 iegions of an embodiment includes configuration through control of the shape and/oi size of the doped souice 20 and/or doped drain 22 iegions of the transistoi. Because only the first portion 18- 1 of the body region is under the gate 16, chaige that may accumulate or an inversion channel that may foim is found only in the first portion 18-1 when the appiopriate control signal is applied to the gate 16. No charge is accumulated and no inversion channel is formed in the second portion 18-2 and/or third portion 18-3 because these portions do not underlie the gate 16 The second portion 18-2 and/or third portion 18-3 therefore cause accumulated charge if any (or inversion channel if formed) to be discontinuous with the source region 20 and/or drain region 22.

As a result of the application of gate voltage to transistoi 14. charge builds up in the first portion 18-1 of the body region 18, but current does not flow in the body region 18 because of the absence of accumulated charge and/or a continuous inversion channel between the souice and drain regions. The discontinuous configuration of the fust portion 18-1 of the body region relative to the source and drain regions therefore acts as an "open circuit" lelative to the flow of curient between the souice 20 and drain 22 regions. Any charge present in the body region 18 thus causes transistor 14 to behave like a capacitoi because the region of chaige in the body 18-1 is disconnected fiom the souice 20 and/or drain 22 regions.

FIGURE 7A shows electrically floating body transistor 14 schematically illustrated as including a MOS capacitor "component" and an intrinsic bipolar transistor "component", under an embodiment. In one aspect, the present inventions employ the intrinsic bipolar transistor "component" to progi am/write as well as read memory cell 12. In this regard, the intiinsic bipolar transistor generates and/or produces a souice or bipolai transistor current which is employed to piogram/write the data state in memory cell 12 and read the data state

of memory cell 12. Notably, in this example embodiment, electrically floating body transistor 14 is an N-channel device. As such, majority carriers 34 are "holes".

The bipolar transistor 14 of an embodiment has a floating body, meaning the potential is not fixed oi "floating". The potential for example depends on the charge at the gate. A conventional bipolar transistor requires each of base current, emitter current, and collector current for proper operation. Any base of the transistor 14 in this embodiment, however, is floating and not fixed because theie is no base contact as found in conventional bipolar FETs; the current in this transistor is therefore refened to herein as a "source" cuπent produced by impact ionization in the body region as described below. FIGURE 7B is an example characteristic curve of electrically floating body tiansistoi 14, under an embodiment. The characteristic curve shows a significant increase in source cuπent (e.g , "log I") at and above a specific threshold value of the potential difference between applied source voltage and applied drain voltage ("souice-drain potential difference"). The ieason for this is that a voltage differential at or above a certain thieshold generates a high electric field in the body region The high electric field iesults in impact ionization in the first portion 18-1 of the body region 18, a process dining which electrons oi paiticles with enough energy generate majority carriers i.e. holes. The impact ionization drives majority carriers to the body region, which increases the body potential, while any minority caπieis flow to the drain (oi source) legion. The inci eased body potential iesults in an increase in souice cuπent in the body region; thus, the excess majority caπieis of the body iegion generate souice current of tiansistoi 14 of an embodiment

FIGURES 8 A and 8B show operation of transistor 14 when writing or piogramming logic "1 ", under an embodiment. The tiansistoi 14 of this embodiment is an N-channel or nMOS FET, but is not so limited; tiansistor 14 may be a P-channel or pMOS FET in an alternative embodiment. The N-channel device includes source 20 and drain 22 regions comprising N+ -type material while the body region 18 comprises a P-type material

A logic "1 ^" programming operation of an embodiment includes a two stage control signal application during which the gate voltage is changed from a first voltage level to a second voltage level. In operation, when writing or programming logic " 1 ", in one embodiment, control signals having predetermined voltages (for example, Vg = 0.5v, Vs = Ov, and Vd = 2.5v) are initially applied during stage one to gate 16, source region 20 and diain region 22 (lespectively) of transistor 14 of memory cell 12 (FIGURE 8A). The stage one control signals may iesult in an accumulation of minority carriers (not shown) in the

electrically floating body 18. As a result of the polarity (e g , positive) of the control signal applied to the gate with the stage one control signals, any minority earners that happen to be present in the body legion 18 accumulate in the first portion 18-1 of the body 18 The minority carriers may accumulate in an area of the first portion 18-1 under the gate, but are not so limited

The physical behavior in the first portion 18-1 of the body 18 in response to the stage one control signals of an embodiment is in contrast to conventional transistor devices in which an inversion channel (also referred to as an ^■ 'N-channer) forms under the gate in an aiea that is close to the inteiface between gate dielectric 32 and electrically floating body 18. The inversion channel is of the same type as the soiiice and drain regions (e.g , N-type in an nMOS FET) and functions to electrically couple the source and drain regions

The inversion channel, however, is not generally formed in the transistor 14 of an embodiment and, additionally, the accumulation of minority carriers in the first portion 18-1 of the body if any is discontinuous with the source 20 and/or diain 22 regions of the device. The reason that no inversion channel is formed in the transistor 14 is because, as the first portion 18-1 ot the body 18 is electrically "disconnected" from the souice 20 and drain 22 legions, the time required to create an inversion channel during a progiamming operation is quite long relative to a writing time for example. Therefore, considering an example writing time of an embodiment approximately in a iange of 1 - 10 nanoseconds, and considering the time requited for generation of an inversion channel in the "disconnected" first portion 18-1 of the body is much longer than 10 nanoseconds, an inversion channel is not generally cieated in the transistor 14 during typical programming operations. Similarly, relatively few or no minority carriers accumulate in the body region.

Furthermore, even if an inversion channel were to form in the first portion 18-1 of the body region as a result of the gate voltage, the inversion channel would not form in the second 18-2 and thiid 18-3 portions of the body region because these regions 18-2/18-3 are not under the gate. Therefore, any inversion channel formed under the embodiments described herein would be "disconnected" from or discontinuous with the source 20 and diain 22 regions The lack of an inversion channel or discontinuous inversion channel (if one were to form) of the transistor of an embodiment is in contrast to conventional transistors in which the inversion channel forms and spreads from the source to the drain and provides conductivity of the transistor. However, the configuration of these conventional devices is such that the gate overlays the entire body region between the source and drain regions, and

the piogramming times aie of a length that ensures formation of an inveision channel when appropiiate voltages are applied, thereby creating a continuous inversion channel that "connects" the source and drain regions upon application of the appropriate polarity signal at the gate. The stage one control signals also generate or provide a source current in electrically floating body region 18 of tiansistoi 14. More specifically, the potential difference between the soui ce voltage and the drain voltage (e.g., 2.5 volts) is greater than the threshold required to turn on the bipolar transistor. Therefore, source current of the transistor causes or pioduces impact ionization and/or the avalanche multiplication phenomenon among particles in the electrically floating body region 18. The impact ionization produces, provides, and/or generates an excess of majority carriers 806 (FIGURE 8B) in the electrically floating body region 18 of transistor 14 of memory cell 12 as described above.

Notably, it is prefeπed that the source current responsible for impact ionization and/oi avalanche multiplication in electrically floating body iegion 18 is initiated or induced by the contiol signal applied to gate 16 of transistor 14 along with the potential difference between the source 20 and diain 22 regions. Such a control signal may induce channel impact ionization which iaises or increases the potential of body iegion 18 and "turns on", produces, causes and/or induces a source current in tiansistor 14. One advantage of the proposed writing/piogramming technique is that a large amount of the excess majority caiiiers 806 may be geneiated and stored in electrically floating body region 18 of tiansistoi 14.

The stage two contiol signals aie subsequently applied to the transistor when writing or programming logic "V as described above. The stage two control signals aie control signals having piedetermined voltages (for example, Vg = -1.Ov, Vs = Ov, and Vd = 2.5v) applied to gate 16, source region 20 and diain iegion 22 (lespectively) of transistor 14 of memory cell 12 (FIGURE 8B) subsequent to stage one. As a result of the polarity (e.g., negative) of the contiol signal applied to the gate with the stage two control signals, the majority cairiers 806 of the body region 18 accumulate near the surface of the first portion 18-1 of the body iegion (FIGURE 8B). The polarity of the gate signal (e.g., negative) combined with the floating body causes he majority cairiers 806 to become trapped oi "stored" near the suiface of the first portion 18-1 of the body region. In this manner the body region 18 of the transistor "stores" charge (e.g., equivalently, functions like a capacitor). Thus, in this embodiment, the predetermined voltages of the stage one and stage

two control signals program or wiite logic "1 " in memoiy cell 12 via impact ionization and/or avalanche multiplication in electrically floating body region 18.

FIGURES 9A and 9B show opeiation of transistor 14 when writing or programming logic "0", under an embodiment. A logic "0" programming operation of an embodiment includes a two stage contiol signal application during which the gate voltage is changed from a fust voltage level to a second voltage level In operation, when writing oi piogramming logic "0", in one embodiment, control signals having piedetermined voltages (for example, Vg = 0 5v, Vs = 0.5v. and Vd = 2 5v) aie initially applied during stage one to gate 16. soui ce region 20 and drain region 22 (respectively) of transistor 14 of memory cell 12 (FIGURE 9A). The stage one control signals may result in an accumulation of minority earners (not shown) in the electrically floating body 18 More specifically, as a result of the polaiity (e g., positive) of the control signal applied to the gate with the stage one contiol signals, any accumulation of minority carriers occurs under the gate 16 in the first poition 18-1 of the body legion, in an area that is close to the inteiface between gate dielectric 32 and electrically floating body 18 as described above. Any minority caniers that accumulate are in the first portion 18-1 of the body iegion as a result of the gate voltage, and thus do not accumulate in the second 18-2 and third 18-3 portions of the body iegion. Therefore, the accumulated chaige of the body region 18 is discontinuous with the source 20 and drain 22 legions. The potential diffeience between the source voltage and the drain voltage (e.g . 2 0 volts) of the stage one control signals, however, is less than the threshold required to turn on tiansistor 14. Consequently, no impact ionization takes place among particles in the body iegion 18 and no bipolar oi source current is produced in the electrically floating body region 18. Thus, no excess of majority carriers are generated in the electrically floating body iegion 18 of transistoi 14 of memory cell 12.

The stage two control signals are subsequently applied to the transistor 14 when writing or programming logic "0" as described above. The stage two control signals are contiol signals having predetei mined voltages (for example. Vg = -1.Ov, Vs = 0.5v, and Vd = 2.5v) applied to gate 16, source region 20 and diain iegion 22 (respectively) of transistoi 14 of memoiy cell 12 (FIGURE 9B) subsequent to stage one. The polarity (e.g., negative) of the gate signal may iesult in any minority carriers that accumulate being removed from electrically floating body region 18 of transistor 14 via one oi more of the source region 20 and the drain region 22. Fuithermore, the polarity of the gate signal (e.g.. negative) causes any minority cairiers remaining in the body region 18 to be trapped or "stored" neai the

sui face of the first portion of the body region 18. The result is an absence of excess majority earners in the body iegion 18 so that, in this manner, the predetermined voltages of the stage one and stage two contiol signals program or write logic "0" in memory cell 12 A logic "0" programming operation of an alternative embodiment includes a two stage contiol signal application during which the gate voltage is changed from a fust voltage level to a second voltage level. In operation, when writing or piogramming logic "0", in this alternative embodiment, control signals having predetermined voltages (foi example, Vg = Ov, Vs = Ov, and Vd = Ov) aie initially applied during stage one to gate 16, source iegion 20 and drain iegion 22 (respectively) of transistor 14 of memory cell 12. The voltage levels described here as contiol signals to implement the write operations are piovided merely as examples, and the embodiments described heiein aie not limited to these voltage levels. The contiol signals increase the potential of electrically floating body iegion 18 which "turns on", produces, causes and/or induces a source current in the tiansistor of the memory cell. In the context of a write operation, the source cuiient generates majority carriers in the electrically floating body iegion which are then stored In the context of a read operation, the data state may be determined primarily by, sensed substantially using and/or based substantially on the source current that is responsive to the lead control signals and significantly less by the interface channel cunent component, which is less significant and/or negligible relatively to the bipolar component Accordingly, the voltage levels to implement the write operations are merely examples of control signals Indeed, the indicated voltage levels may be relative or absolute Alternatively, the voltages indicated may be relative in that each voltage level, for example, may be increased or decreased by a given voltage amount (foi example, each of the gate, source, and drain voltage may be increased or decreased by 0.5, 1.0 and 2 0 volts) whether one or more of the voltages (foi example, the source, drain or gate voltages) become or aie positive and negative.

In one embodiment, the memory cell 12 may be implemented in a memory cell array. When a memory cell is implemented in a memory cell array configuration, it may be advantageous to implement a "holding" operation or condition to certain memoiy cells when piogramming one oi more other memoiy cells of the an ay in order to impiove or enhance the retention chaiacteristics of such certain memory cells. In this regard, the transistor of the memory cell may be placed in a "holding" state via application of control signals (having predetermined voltages) which are applied to the gate and the source and

drain regions of the transistor of the memory cells which are not involved in the write or read opeiations.

For example, with reference to FIGURE 10, such control signals provide, cause and/or induce majority carrier accumulation in an area that is close to the interface between gate dielectric 32 and electrically floating body 18. In this embodiment, it may be preferable to apply a negative voltage to gate 16 where transistor 14 is an N-channel type transistoi 14. The proposed holding condition may provide enhanced retention characteristics.

With reference to FIGURE 1 1 , in one embodiment, the data state of memory cell 12 may be read and/or determined by applying control signals having predetermined voltages to gate 16 and source region 20 and drain region 22 of transistor 14 (for example, Vg = - 1.Ov, Vs = Ov and Vd = 2.5v, respectively). Such control signals, in combination, induce and/or cause a source cuirent in memory cells 12 that are programmed to logic " 1 " as described above. As such, sensing circuitry (for example, a cross-coupled sense amplifier), which is coupled to transistor 14 (for example, drain region 22) of memory cell 12, senses the data state using primarily and/or based substantially on the souice cuπent. Notably, for those memory cells 12 that are programmed to logic "0", such control signals induce, cause and/or pioduce little to no source current (for example, a considerable, substantial or sufficiently measuiable source current). Thus, in response to lead control signals, electrically floating body tiansistor 14 geneiates a source cuπent which is representative of the data state of memory cell 12. Where the data state is logic high or logic "1 ", electrically floating body transistor 14 provides a substantially greater souice current than where the data state is logic low oi logic "0". Electrically floating body transistor 14 may provide little to no source current when the data state is logic low or logic "0". As discussed in more detail below, data sensing circuitiy determines the data state of the memory cell based substantially on the source current induced, caused and/or produced in iesponse to the lead control signals.

The voltage levels described here as control signals to implement the read operations are provided merely as examples, and the embodiments described herein are not limited to these voltage levels. The indicated voltage levels may be relative or absolute.

Alternatively, the voltages indicated may be relative in that each voltage level, for example, may be increased or decreased by a given voltage amount (for example, each voltage may be incieased or decreased by 0.5, 1.0 and 2.0 volts) whether one or more of the voltages (for example, the source, drain or gate voltages) become or are positive and negative.

FIGURE 12 is a plot of voltage levels versus time for examples of each of write "0", wiite "1 ", and iead operations, under an embodiment. These examples are described in detail above The voltage levels for each of the source and diain are interchangeable as a result of the MOSFET being a symmetrical device; therefore, voltage levels shown or described herein as applied to the source can be applied to the drain, while voltage levels shown oi desciibed herein as applied to the drain can be applied to the source.

As described above with reference to FIGURE 6. electrically floating body transistor 14 includes a body iegion 18 configuied to be electrically floating. The body region 18 includes three portions or regions 18-1/18-2/18-3 that collectively define the electrically floating body 18 The transistor 14 includes a gate 16 disposed over the first portion 18-1 of the body region 18 A source region 20 adjoins a second portion 18-2 of the body region 18, and a drain region 22 adjoins a third portion 18-3 of the body region 18; the second portion 18-2 and thiid portion 18-3 of the body region 18 each adjoin the fust portion 18- 1. Consequently, the second portion 18-2 and third portion 18-3 of the body iegion function to "disconnect" any charge that may accumulate and/or any inversion channel that may form in the first portion 18-1 from one or more of the source 20 and the drain 22.

FIGURE 13 is a flow diagram for forming transistor 14, under an embodiment. Tiansistor 14 is formed, geneially, by forming 1302 a semiconductor on an insulatoi An insulating layei and a gate is fonned 1304 over a fust portion of the semiconductor. Spaceis are formed 1306 over a second portion and a third portion of the semiconductor, and the spaceis adjoin the insulating layer. The first portion, second portion, and third portion of the semiconductor collectively form the floating body region. Formation of transistor 14 continues by foiming 1308 a source region through implantation of an impurity into a fourth portion of the semiconductor after forming the spacers. The fourth portion of the semiconductor is adjacent the second portion. A drain region is also formed 1308 by implanting the impurity into a fifth portion of the semiconductor aftei forming the spacers The fifth portion of the semiconductor is adjacent the thiid portion.

More specifically, in fabricating transistor 14, the gate is defined and used as a mask during implantation of the semiconductor to form the source and drain regions of the device. The spacers are then formed prior to any implantation or doping of the semiconductor so that all implantation of the seniiconductoi (e.g., implantation to form the source and diain) is performed aftei foimation of the spaceis. This is in contrast to conventional semiconductor processes in which a gate is fonned, followed by a first implantation process (e.g , to foim a lightly-doped portion of the source and drain regions), followed by

formation of the spaces, and followed by a second implantation process (e.g , to form a highly-doped poition of the souice and diain regions).

As a iesult of implanting only after formation of the spacers, the doping profiles that iesult in creation of the source and/or diain region are configured so that the body region includes the second 18-2 and/oi third 18-3 portions and thus extends beyond an extended lateral boundary of the gate. The second 18-2 and/or thiid 18-3 portions of the body region function to prevent any inversion channel formation through the entire body region of the device because the area of the body region in which the channel forms under the gate is not continuous with the souice and drain regions, as desciibed above. Therefore, upon application of a gate voltage that is appropriate to material of the body region, charge accumulates in the body iegion of the device, but current cannot flow between the source and diain legions because no inveision channel is formed between the source and/or diain and any accumulated charge is disconnected from the source and/or drain

The tiansistoi devices of various alternative embodiments can provide a discontinuous region of any accumulated charge in the body by disconnecting the first portion of the body as described herein at the source region, the diain region, or both the souice and drain legions. Fuithei, various doping densities (e.g., very light, light, high, and very high doping) and/or profiles can be used in the source, body, and drain regions of the transistoi 14. Examples follow of various alternative embodiments. FIGURE 14 shows an electrically floating body transistor 14 in which the first poition 18-1 of the body region is made discontinuous with only the drain by a third portion 18-3 of the body iegion, under an embodiment.

FIGURE 15 shows an electrically floating body transistor 14 in which the first portion 18-1 of the body region is made discontinuous with only the drain by a thiid portion 18-3 of the body iegion, undei an embodiment. The souice iegion includes a highly-doped (HD) portion and a lightly-doped (LD) portion.

FIGURE 16 shows an electrically floating body transistor 14 in which the first portion 18-1 of the body region is made discontinuous with only the source by a second portion 18-2 of the body region, undei an embodiment. FIGURE 17 shows an electrically floating body transistor 14 in which the first portion 18-1 of the body region is made discontinuous with the only the source by a second portion 18-2 of the body iegion, under an embodiment. The drain region includes a highly- doped portion and a lightly-doped portion.

FIGURE 18 shows an electrically floating body transistor 14 in which the first portion 18- 1 of the body region is made discontinuous with both the source and drain regions, and each of the source and drain regions comprise LD and/or HD portions, under an embodiment. FIGURE 19 shows an electrically floating body tiansistor 14 in which the first portion 18-1 of the body region is made discontinuous with both the souice and diain regions, and each of the source and drain regions aie LD, under an embodiment.

FIGURE 20 shows an electrically floating body tiansistor 14 in which the first portion 18-1 of the body region is made discontinuous with both the source and drain regions, and the souice region is LD and the drain region is HD, under an embodiment

FIGURE 21 shows an electiically floating body transistor 14 in which the first portion 18- 1 of the body region is made discontinuous with both the souice and drain regions, and the souice region is HD and the drain region is LD, under an embodiment.

FIGURE 22 shows an electiically floating body transistor 14 in which the first portion 18-1 of the body region is made discontinuous with both the source and drain regions, and each of the souice and drain regions are HD, under an embodiment

The progiamming techniques desciibed above may consume less power lelative to conventional techniques (e.g , FIGURES 4A and 4B). The reduced power consumption relates to the piogiamming techniques of the present inventions being implemented without employing a back gate terminal (Compare, FIGURE 4C), thereby reducing or eliminating the flow of any source current in the device when the device is in an "off state. Furthermore, the current for wiiting or programming to logic "0" may be smaller when compaied to such conventional techniques

The gate oxide thickness in conventional devices is requiied to be substantial in older to not be bioken down by the high electric field potential. The high electric field potential results fiom the relatively high potential difference required between the source and diain regions during write operations. In contrast, however, the embodiments of transistor 14 desciibed herein pioduce a relatively lower potential diffeience between the souice and drain regions during write operations. The lower potential difference results from the device configuiation desciibed above which includes an increased distance between the souice and drain regions resulting from the configuration (e.g., size, shape, etc ) of the source and diain regions relative to the gate region Because the electric field potential is i educed significantly with this design, the gate oxide region can be thinner.

As mentioned above, the present inventions may be implemented in an integiated circuit device (fot example, a discrete memory device oi a device having embedded memory) including a memory array having a plurality of memoiy cells arranged in a plurality of lows and columns wherein each memory cell includes an electrically floating body tiansistoi The memoiy arrays may comprise N-channel, P -channel and/or both types of tiansistors Indeed, circuitry that is peripheral to the memory aπay (for example, data sense circuitiy (for example, sense amplifiers or comparators), memory cell selection and control circuitiy (foi example, word line and/or source line drivers), as well as low and column addiess decodeis) may include P-channel and/or N-channel type transistois For example, with reference to FIGURES 23 A and 23B. the integrated circuit device may include array 10, having a plurality of memory cells 12, data write and sense circuitiy 36. and memory cell selection and contiol circuitry 38 The data write and sense circuitry 36 reads data fiom and writes data to selected memory cells 12. In one embodiment, data write and sense circuitry 36 includes a plurality of data sense amplifiers. Each data sense amplifiei leceives at least one bit line 32 and an output of reference generator circuitiy (for example, a current or voltage refeience signal) In one embodiment, the data sense amplifier may be a cioss-coupled type sense amplifier as described and illustiated in U. S Patent 7,301 ,838. filed by Waller and Carman, on December 12, 2005, and entitled "Sense Amplifiei Circuitry and Architectuie to Write Data into and/or Read Data from Memory Cells", the application being incorporated herein by reference in its entirety) to sense the data state stored in memory cell 12 and/or wiite-back data into memory cell 12

The data sense amplifier may employ voltage and/or current sensing ciicuitiy and/oi techniques. In the context of current sensing, a current sense amplifier may compare the current from the selected memoiy cell to a ieference current, for example, the cuπent of one oi more reference cells From that comparison, it may be determined whether memoiy cell 12 contained logic high (relatively more majority caπies 34 contained within body region 18) oi logic low data state (relatively less majority carries 28 contained within body region 18). Notably, the present inventions may employ any type or form of data write and sense circuitry 36 (including one or moie sense amplifiers, using voltage oi current sensing techniques, to sense the data state stored in memory cell 12) to iead the data stored in memoiy cells 12 and/or write data in memory cells 12.

Memory cell selection and control circuitry 38 selects and/or enables one or more predetermined memoiy cells 12 to facilitate reading data from and/or writing data to the memory cells 12 by applying a control signal on one or more word lines 28. The memory

cell selection and control circuitry 38 may generate such control signals using address data, for example, row address data Indeed, memory cell selection and control circuitry 38 may include a conventional word line decoder and/or driver. There are many different contiol/selection techniques (and circuitry) to implement the memory cell selection technique. Such techniques, and circuitry, are well known to those skilled in the art. All such contiol/selection techniques, and circuitry, whether now known or later developed, are intended to fall within the scope of the present inventions.

The present inventions may be implemented in any aichitectuie, layout, and/oi configuration comprising memory cells having electrically floating body tiansistors. For example, in one embodiment, memory airay 10 including a plurality of memory cells 12 having a separate souice line for each row of memoiy cells (a iow of memory cells includes a common word line connected to the gates of each memory cell of the row). (See, for example, FIGURES 24, 25 and 26). The memory anay 10 may employ one or more of the example piogramming, leading and/or holding techniques described above. In one embodiment, the present inventions are implemented in conjunction with a two step write opeiation whereby all the memoiy cells of a given row are written to a pi edetei mined data state by first executing a "clear" operation, wheieby all of the memory cells of the given iow are written or programmed to logic "0", and thereafter selective memory cells of the row are selectively write operation to the predetermined data state (here logic "1 "). The piesent inventions may also be implemented in conjunction with a one step write operation whereby selective memory cells of the selected row are selectively written oi progiammed to eithei logic " 1 " oi logic "0" without first implementing a "clear" operation.

With ieference to FIGURES 24 and 25, memory cells 12 may be programmed using the two step operation wherein a given row of memory cells are written to a fust piedetermined data state by fust executing a "clear" operation (which, in this example embodiment, all of the memory cells of the given row are written or programmed to logic "0") and thereaftei selected memory cells are written to a second predetermined data state (i.e . a selective write opeiation to the second predetermined data state). The "clear" operation may be performed by writing or piogramming each memory cell of the given iow to a fust piedetermined data state (in this example embodiment the first predetermined data state is logic "0") using the inventive technique described above.

In particular, transistor of each memory cell 12 of a given row (foi example, memory cells 12a- 12d) is controlled to store logic "0". In this regard, stage one and stage

two control signals to implement a clear operation as described above are applied to the gate, the source iegion and the drain region of the transistor of memory cells 12a- 12d. In response, the same logic state (for example, logic low or logic "0") is stored in memory cells 12a-12d and the state of memory cells 12a-12d aie "cleared". Theieafter, selected memory cells of the given row may be programmed to the second predeteimined logic state. In this legard, the transistors of certain memory cells of a given low are written to the second predetermined logic state in older to store the second piedetermined logic state in memory cells. For example, with refeience to FIGURE 25, memoiy cells 12b and 12c aie progiammed to logic high or logic "1 " by applying (i) 0.5v to the gate (via woid line 28,), (ii) Ov to the source region (via source line 3O ₁ ), and (iii) 2.5v to the diain region (via bit line 32,+i and 32,+ ₂ ), followed by application of -1.Ov to the gate (via woid line 2S ₁ ). In paiticulai, such control signals generate or provide an excess of majority caiiiers in the electrically floating body iegion of the transistor of memoiy cells 12b and 12c which corresponds to logic high or logic " 1 ". As mentioned above, it is preferred that the souice cuirent responsible foi impact ionization and/oi avalanche multiplication in the floating body is initiated or induced by the control signal (control pulse) applied to the gate of the transistoi Such a signal/pulse may induce the channel impact ionization which raises or increases the potential of the electrically floating body iegion of the transistoi of memoiy cells 12b and 12c and "turns- on" and/or pioduces a source cuπent in transistor 14. One advantage of the proposed method is that a large amount of the excess majority canϊeis may be generated and stoied in the electrically floating body region of the transistor of memory cells 12b and 12c

Notably, in this example embodiment, memory cells 12a and 12d aie maintained at logic low (or logic "0") by applying an inhibit control signal to the drain iegion of each memory cell 12a and 12d. For example, applying Ov to the drain legions of memory cells 12a and 12d (via bit lines 32, and 32 _l+4 ) inhibits writing logic high or logic " 1 " into memoiy cells 12a and 12d during the selective write operation for memory cells 12b and 12c. A "holding" operation or condition may be used for the other memory cells in memory cell array 10 to minimize and/or reduce the impact of the write operation for memory cells 12a-12d connected to woid line 28,. With reference to FIGURES 24 and 25, in one embodiment, a holding voltage is applied to the gates of the transistors of othei memory cells of memory cell array 10 (for example, each memoiy cell connected to word lines 28, ₊ i, 28, ₊₂ , 28,+ ₃ , and 28,+j). In one example embodiment, a holding voltage of -1.2v is applied to the gate of each transistor of the memory cells connected to word lines 28,+|,

28,+ ₂ , 28,+3, and 28,+ ₄ . In this way, the impact of the write operation of memoiy cells 12a- 12d (which are connected to word line 28,) on the other memory cells of memory cell atray 10 is minimized and/or reduced.

A selected row of memory cells may be read by applying read control signals to the associated word line 28 and associated source lines 30 and sensing a signal (voltage and/oi current) on associated bit lines 32. In one example embodiment, with reference to FIGURE 26, memoiy cells 12a-12d are read by applying (i) -1.Ov to the gate (via word line 28,), (ii) Ov to the source legion (via souice line 30,) and (iii) 2.5v to the drain region (via bit line 32,+i and 32,+τ). The data write and sense circuitry 36 reads the data state of the memory cells 12a-12d by sensing the response to the applied iead control signals. In iesponse to the lead control signals, memory cells 12a-12d generate a source cuπent which is representative of the data state of memoiy cells 12a-12d. In this example, memory cells 12b and 12c (which were eailiei progiammed to logic " 1 "), in response to the read control signals, geneiate a souice current which is considerably larger than any channel cuiient In contrast, memory cells 12a and 12d (which were earliei programmed to logic "0"), such control signals induce, cause and/or produce little to no source cuπent (for example, a considerable, substantial or sufficiently measurable source current). The sense circuitiy 36 senses the data state using piimarily and/or based substantially on the source cuπent

Thus, in iesponse to lead control signals, the electrically floating body transistoi of each memory cell 12a-12d generates a source current which is representative of the data state stored theiein. The data sensing circuitry in data write and sense ciicuitiy 36 determines the data state of memory cells 12a-12d based substantially on the source cuπent induced, caused and/or produced in response to the read control signals Notably, as mentioned above, a iead opeiation may be performed by applying other control signaling techniques.

Again, it may be advantageous to employ a "holding" operation or condition foi the other memory cells in memory cell aiτay 10 to minimize and/or reduce the impact of the read operation of memory cells 12a-12d. With continued refeience to FIGURE 26. in one embodiment, a holding voltage is applied to the gates of the transistors of other memory cells of memoiy cell anay 10 (for example, each memory cell connected to word lines 28 _I+ |, 28,+ ₂ , 28|- _H , and 28,+ ₄ ). In one example embodiment, a holding voltage of -1.2v is applied to the gate of each transistor of the memory cells connected to woid lines 28,+!. 28, ₊₂ , 28,+3. and 28, ₊₄ . In this way. the impact of the read opeiation of memoiy cells 12a-12d (which are

connected to woid line 28,) on the other memory cells of memoiy cell anay 10 is minimized and/or reduced.

The programming and reading techniques described herein may be used in conjunction with a plurality of memory cells aπanged in an array of memory cells A memoiy array implementing the structure and techniques of the present inventions may be controlled and configured including a plurality of memory cells having a separate souice line for each iow of memory cells (a row of memory cells includes a common word line). The memoiy anay may use any of the example programming, holding and/or reading techniques desciibed herein. The memoiy arrays may comprise N-channel, P-channel and/or both types of transistors. Circuitry that is peripheral to the memory anay (foi example, sense amplifieis or comparators, row and column address decodeis, as well as line driveis (not illustrated herein)) may include P-channel and/or N-channel type transistors. Where P-channel type tiansistors aie employed as memory cells in the memory aiτay(s), suitable write and iead voltages (foi example, negative voltages) are well known to those skilled in the art in light of this disclosuie.

The piesent inventions may be implemented in any electrically floating body memoiy cell and memory cell airay. Foi example, in certain aspects, the piesent inventions are directed to a memory array, having a plurality of memory cells each including an electrically floating body transistor, and/or technique of progiamming data into one or moie memory cells of such a memory cell array. In this aspect of the inventions, the data states of adjacent memoiy cells and/oi memory cells that share a word line may or may not be individually programmed.

With reference to FIGURES 23A and 23B, memoiy anay 10 may compiise a pluiality of memory cells 12 of N-channel type, P-channel type and/or both types of electrically floating body transistors. The memory airay 10 includes a plurality of lows and columns (foi example, in a matrix foim) of memory cells 12.

The chcuitry which is peripheial to memory array 10 (for example, data write and sense ciicuitry 36 (such as, for example, sense amplifiers oi comparators), memory cell selection and contiol circuitry 38 (such as, for example, address decoders and word line diivers)) may include P-channel type and/or N-channel type transistors. Where N-channel type transistois or P-channel type transistors are employed as memory cells 12 in memoiy aiτay(s) 10, suitable wiite voltages are known to those skilled in the art.

As mentioned above, memory cells 12 (having electrically floating body transistor 14) and memory cell anay 10 of the present inventions may be implemented in an

integrated circuit device having a memory portion and a logic portion (see, for example, FIGURE 23A), or an integrated circuit device that is primarily a memory device (see, foi example. FIGURE 23B) Indeed, the present inventions may be implemented in any device having one or more memory cells 12 (having electrically floating body transistors) and/or memoiy cell airays 10. For example, with reference to FIGURE 23A, an integiated circuit device may include array 10, having a plurality of memory cells 12 (having electrically floating body transistors), data write and sense circuitry, and memory cell selection and control ciicuitry (not illustrated in detail). The data write and sense circuitry writes data into and senses the data state of one or more memory cells. The memory cell selection and control ciicuitry selects and/or enables one or more predetermined memory cells 12 to be read by data sense circuitry during a read operation

For example, the electrically floating body transistor, which programmed (written to), controlled and/or read using the techniques of the present inventions, may be employed in any electrically floating body memory cell, and/or memory cell array architecture, layout, structuie and/or configuration employing such electrically floating body memory cells In this regard, an electrically floating body transistor, which state is read using the techniques of the present inventions, may be implemented in the memory cell, architectuie, layout, structure and/or configuration described and illustrated in the following U.S. patents and non-provisional U.S. patent applications: (1 ) U.S Patent 6,969,662, which was filed by Fazan et al. on June 10, 2003 and entitled "Semiconductor Device";

(2) U S. Patent 7,061 ,050, which was filed by Fazan et al. on February 18, 2004 and entitled "Semiconductor Device";

(3) U.S Patent 7.085, 153. which was filed by Ferrant et al. on April 22. 2004 and entitled "Semiconductor Memory Cell, Array, Architecture and Device, and Method of

Operating Same";

(4) U.S. Patent 7.187.581 , which was filed by Ferrant et al. on March 14, 2005 and entitled "Semiconductor Memory Device and Method of Opeiating Same", and which is a divisional application of U.S. Patent Application Serial No. 10/840,009 (now abandoned), (5) U.S. Patent 7,184,298, which was filed by Fazan et al. on September 15, 2004 and entitled "Low Power Programming Technique for a One Transistor SOI Memory Device & Asymmetrical Electrically Floating Body Memory Device, and Method of Manufacturing Same";

(6) U. S Patent Application Serial No. 1 1/724.552, which was filed by Caiman on Maich 15, 2007 and entitled "Memory An ay Having a Programmable Word Length, and Method of Operating Same" (U.S. Patent Application Publication No. 2007/0285982);

(7) U. S Patent Application Serial No. 1 1/787.718, which was filed by Popoff on April 17, 2007 and entitled "Semiconductor Memory An ay Architecture, and Method of

Controlling Same" (U.S. Patent Application Publication No. 2007/0241405); and

(8) U.S. Patent Application Serial No. 1 1/821 ,848. which was filed by Fisch et al. on June 26, 2007 and entitled "Integrated Circuit Including Memory Atray Having a Segmented Bit Line Architecture and Method of Controlling and/or Operating Same" (LlS Patent Application Publication No. 2008/0013359)

Notably, the memory cells may be controlled (for example, programmed or read) using any of the control circuitiy described and illustrated in the above-referenced eight (8) U.S. patents and patent applications. For the sake of brevity, those discussions will not be repeated, such control circuitiy is incorporated herein by refeience. Indeed, all memory cell selection and control circuitry for programming, reading, controlling and/or operating memory cells including electrically floating body transistors, whether now known or later- developed, are intended to fall within the scope of the present inventions.

Moreover, the data write and data sense circuitry may include a sense amplifier (not illustrated in detail herein) to read the data stored in memory cells 12. The sense amplifier may sense the data state stored in memory cell 12 using voltage or current sensing circuitiy and/oi techniques In the context of a current sense amplifier, the current sense amplifier may compare the cell current to a reference current, for example, the cuirent of a reference cell (not illustrated). From that comparison, it may be determined whether memory cell 12 contained logic high (relatively more majority carriers 34 contained within body region 18) or logic low data state (relatively less majority carriers 34 contained within body iegion 18). Such circuitiy and configurations thereof are well known in the ait.

In addition, the present inventions may employ the reference generation techniques (used in conjunction with the data sense circuitry for the read operation) described and illustrated in U S. Patent Application Serial No. 1 1/515,667, "Method and Circuitry to Generate a Reference Cuπent for Reading a Memory Cell, and Device Implementing Same" filed Septembei 5, 2006 by Bauser, and claiming the benefit of U.S. Provisional Patent Application Serial No. 60/718,417, which was filed by Bauser on September 19. 2005, and entitled "Method and Circuitry to Generate a Reference Current for Reading a Memory Cell Having an Electrically Floating Body Transistor, and Device Implementing Same" The

entile contents of the U S. Patent Application Serial No. 1 1/515,667 aie incorporated herein by reference. Further, the present inventions may also employ the iead circuitry and techniques described and illustrated in U.S. Patent 6,912,150, which was filed by Portmann et al. on May 7, 2004, and entitled "Reference Cuirent Generator, and Method of Pi ogramming. Adjusting and/or Operating Same". The contents of U. S Patent 6,912.150 aie heieby incoiporated by reference herein.

It should be further noted that while each memory cell 12 in the example embodiments (described above) includes one transistoi 14, memory cell 12 may include two transistois, as described and illustrated in U.S. Patent 7,085, 153, which was filed by Ferrant et al on Apiil 22, 2004 and entitled "Semiconductor Memory Cell, Array, Architecture and Device, and Method of Operating Same". The contents of U.S. Patent 7,085.153 aie hereby incoiporated by reference herein.

Moreover, the present inventions may be components of or integrated with multi-bit memoiy cell applications as described in U. S Non-Piovisional Patent Application Serial No 1 1/703,429. which was filed by Okhonin on February 7, 2007, and entitled "Multi-Bit Memory Cell Having Electrically Floating Body Transistor, and Method of Progiamming and Reading Same" (U.S Patent Application Publication No. 2007/0187775)

The electrically floating memory cells, transistors and/or memoiy array(s) may be fabiicated using well known techniques and/or materials. Indeed, any fabrication technique and/or material, whethei now known oi later developed, may be employed to fabricate the electrically floating memory cells, tiansistors and/or memory array(s). For example, the present inventions may employ silicon, germanium, silicon/germanium, gallium aisenide oi any other semiconductor material (whether bulk-type or SOI) in which transistois may be formed. As such, the electrically floating memory cells may be disposed on or in (collectively "on") SOI-type substrate or a bulk-type substrate.

Indeed, the electrically floating transistors, memory cells, and/oi memoiy aiτay(s) may employ the techniques described and illustrated in non-provisional patent applications entitled "Integiated Ciicuit Device, and Method of Fabricating Same", which was filed on July 2. 2004, by Fazan, Serial No. 10/884,481 (U.S Patent Application Publication No. 2005/0017240), and "One Transistor Memory Cell having a Strained Electrically Floating Body Region, and Method of Operating Same", which was filed on October 12, 2006, by Bassin, Serial No 1 1/580,169 (U.S. Patent Application Publication No 2007/0085140). and/or "Memory Cell and Memory Cell Array Having an Electrically Floating Body Transistoi. and Methods of Operating Same", by Okhonin, Serial No 1 1/509.188 (U.S

Patent Application Publication No 2007/0058427), which claims the benefit of piovisional patent application entitled "Memory Cell, Array and Device, and Method of Operating Same", which was filed on October 19. 2005, Serial No. 60/728,061 , by Okhonin et al. (hereinafter collectively "Integiated Ciicuit Device Patent Applications"). The contents of the Integrated Ciicuit Device Patent Applications are heieby incorporated by reference herein.

Memory anay 10 (including SOI memory tiansistois) further may be integrated with SOI logic transistors, as desciibed and illustiated in the Integrated Circuit Device Patent Applications. For example, in one embodiment, an integrated circuit device includes memory section (having, for example, partially depleted (PD) or fully depleted (FD) SOI memoiy transistors 14) and logic section (having, for example, high performance tiansistors, multiple gate tiansistors, and/or non-high performance transistois (for example, single gate transistors that do not possess the peiformance characteristics of high perfoimance transistors) Further, memory array(s) 10 may be comprised of N-channel, P-channel and/or both types of transistors, as well as partially depleted and/or fully depleted type transistois. For example, circuitry that is peripheral to the memoiy array (for example, sense amplifiers or compaiators. row and column address decoders, as well as line drivers (not illustiated heiein)) may include FD-type transistors (whether P-channel and/or N-channel type) Alternatively, such circuitiy may include PD-type transistois (whether P-channel and/or N- channel type). Theie aie many techniques to integiate both PD and/or FD -type tiansistors on the same substrate (see, for example, U.S. Patent 7,061 ,050, which was filed by Fazan et al. on February 18, 2004 and entitled "Semiconductoi Device"). All such techniques, whether now known or latei developed, aie intended to fall within the scope of the present inventions. Where P-channel type transistors are employed as memory cells 12 in the memory arτay(s), suitable write and lead voltages (for example, negative voltages) are well known to those skilled in the ait in light of this disclosure.

Notably, electrically floating body transistor 14 may be a symmetrical or nonsymmetrical device Where transistor 14 is symmetrical, the source and drain regions are essentially interchangeable. However, wheie transistor 14 is a non-symmetrical device, the source or drain regions of tiansistor 14 have different electrical, physical, doping concentration and/oi doping profile characteristics. As such, the source or drain legions of a non-symmetrical device are typically not interchangeable. This notwithstanding, the drain iegion of the electrically floating N-channel transistor of the memory cell (whethei the

source and diain legions are interchangeable or not) is that region of the transistor that is connected to the bit line/sense amplifier

Aspects of the present inventions described herein, and/or embodiments thereof, may include a semiconductor device comprising one or more of: a body region configured to be electrically floating; a gate disposed over a first poition of the body region; a source region adjoining a second portion of the body region, the second portion adjacent the first portion and separating the source region from the first portion; and a drain region adjoining a third portion of the body region, the third poition adjacent the first portion and separating the drain legion from the fust portion. The device of an embodiment includes a first voltage coupled to the gate. The fust voltage may cause minority carriers to accumulate in the first portion of the body region

The minority carriers that may accumulate in an embodiment accumulate at a surface region of the first portion of body region that is juxtaposed or near a gate dielectric which is disposed between the gate and the first portion of the body region. The region of the device of an embodiment that includes the minority carriers is disconnected from the source region by the second portion of the body region.

The region of the device of an embodiment that includes the minority carriers is disconnected from the drain region by the third portion of the body region.

The device of an embodiment includes a first potential difference coupled between the source and the diain, the first potential difference generating source current as a result of impact ionization induced by the minority carriers.

The device of an embodiment includes a second voltage coupled to the gate after and instead of the first voltage, the second voltage causing an accumulation of majority carriers in the first portion of the body region, wherein the majority carriers result in the first data state which is representative of a first charge in the body region.

The device of an embodiment includes a second potential difference coupled between the source and the drain, the second potential difference resulting in a second data state which is representative of a second charge in the body region.

The device of an embodiment includes an insulating layer disposed between the gate and the body region

The body region of the device of an embodiment includes a first type of semiconductor material.

The source region and drain region of the device of an embodiment includes a second type of semiconductor material.

The source iegion of the device of an embodiment includes a lightly doped region.

The source iegion of the device of an embodiment includes a highly doped region.

The source region of the device of an embodiment includes a lightly doped region and a highly doped region The drain region of the device of an embodiment includes a lightly doped region.

The diain region of the device of an embodiment includes a highly doped region.

The drain region of the device of an embodiment includes a lightly doped iegion and a highly doped region

Aspects of the present inventions desciibed herein, and/or embodiments theieof, may include a semiconductoi device comprising one or more of: a gate, a body region partially disposed under the gate and electrically floating; and a source region and a drain region adjacent the body region, wherein one or more of the souice region and the drain iegion include a doped region shaped so that a farthermost boundaiy of the doped region is separated fiom a portion of the body region underlying the gate. Aspects of the present inventions described herein, and/or embodiments thereof, may include a semiconductor device comprising one or more of: a gate; a body region configured as an electrically floating body, the body region configured so that material foiming the body iegion extends beyond at least one lateral boundaiy of the gate; and a source iegion and a drain region adjacent the body region. Aspects of the piesent inventions described herein, and/or embodiments thereof, may include a tiansistor comprising one or moie of. a floating body region on a insulating substrate, a gate disposed over a portion of the floating body iegion; and a source region and a chain region, wherein a doping profile of one or more of the source and the diain iegion is configured to prevent formation of a contiguous cunent channel extending between the source region and the drain region thiough the floating body region.

Aspects of the piesent inventions described herein, and/or embodiments theieof, may include a method for forming a transistor, comprising one or more of: forming a semiconductor on an insulator; foiming an insulating layer and a gate over a first portion of the semiconductor; foiming spacers over a second portion and a third portion of the semiconductor, the spaceis adjoining the insulating layer, wherein the first portion, second portion, and third portion form a floating body region; forming a source region by implanting an impurity into a fourth portion of the semiconductoi after forming the spacers, the fourth portion adjacent the second portion; and forming a drain region by implanting the

impurity into a fifth portion of the semiconductor after forming the spacers, the fifth portion adjacent the third portion.

The body region formed under the method of forming a transistor of an embodiment comprises a first type of semiconductor material. The source iegion and drain region formed under the method of forming a transistor of an embodiment each comprise a second type of semiconductor material that is different from the first type

Implanting the impurity into the fourth portion under the method of forming a transistor of an embodiment includes implanting to form a lightly doped source region. Implanting the impurity into the fourth portion undei the method of forming a tiansistoi of an embodiment includes implanting to form a highly doped source iegion.

Implanting the impuiity into the fourth portion under the method of forming a tiansistor of an embodiment includes implanting to form a source region that includes both a lightly doped souice portion and a highly doped source portion. Implanting the impurity into the fifth portion undei the method of forming a transistor of an embodiment includes implanting to form a lightly doped drain region

Implanting the impurity into the fifth portion under the method of forming a tiansistoi of an embodiment includes implanting to form a highly doped drain region

Implanting the impurity into the fifth portion under the method of forming a transistor of an embodiment includes implanting to form a drain iegion that includes both a lightly doped drain portion and a highly doped drain portion.

Aspects of the present inventions described herein, and/or embodiments theieof, may include a method for foiming an integrated circuit device, the method comprising one or more of. foiming a semiconductor on an insulator; forming an insulating layer and a gate over a first portion of the semiconductor; forming spacers over a second portion and a third portion of the semiconductor, the spacers adjoining the insulating layei, wheiein the first portion, second portion, and third portion form a floating body region; forming a source region by implanting an impuiity into a fourth portion of the semiconductor after forming the spacers, the fourth portion adjacent the second portion; and forming a drain iegion by implanting the impurity into a fifth portion of the semiconductor after forming the spacers, the fifth portion adjacent the thiid portion.

Aspects of the present inventions described herein, and/or embodiments thereof, may include a method for forming a semiconductor device, the semiconductor device produced by the method comprising one oi more of; a body region configured to be

electrically floating; a gate disposed over a first portion of the body region; a source region adjoining a second portion of the body region, the second portion adjacent the first portion and separating the source region from the first portion; and a drain region adjoining a third portion of the body legion, the third portion adjacent the first portion and separating the drain region from the first portion.

Aspects of the present inventions described heiein. and/or embodiments thereof, may include an integrated circuit device comprising one oi more of: a memory cell including a transistoi, the transistor comprising one or more of a body region configuied to be electrically floating, a gate disposed over a first portion of the body region, a source region adjoining a second portion of the body region, the second portion adjacent the first portion and separating the source region fiom the first portion, and a drain region adjoining a third portion of the body legion, the third portion adjacent the fust portion and separating the drain region fiom the first portion; wherein the memory cell includes a fust data state repiesentative of a first charge in the fust portion of the body legion, wherein the memory cell includes a second data state representative of a second charge in the first portion of the body legion; data wiite circuitry coupled to the memoiy cell, the data wiite circuitry configuied to apply fiist wiite control signals to the memoiy cell to wiite the fust data state and second write control signals to the memory cell to write the second data state, wherein, in response to first write control signals, the electrically floating body tiansistor generates a fust source current which substantially provides the first charge in the first portion of the body region.

The fust write control signals of the integrated circuit device of an embodiment cause, piovide, pioduce and/or induce the first source current.

The first write contiol signals of the integiated ciicuit device of an embodiment include a signal applied to the gate and a signal applied to the source region, wherein the signal applied to the gate includes a first voltage having a first amplitude and a second voltage having a second amplitude.

The first write control signals of the integrated circuit device of an embodiment include a signal applied to the gate and a signal applied to the drain region, wherein the signal applied to the gate includes a fust voltage having a fust amplitude and a second voltage having a second amplitude.

The fust write control signals of the integiated circuit device of an embodiment include a potential difference applied between the source iegion and the drain legion.

The first vviite control signals of the integrated circuit device of an embodiment include a signal applied to the gate, wherein the signal applied to the gate includes a first voltage having a first amplitude and a second voltage having a second amplitude

The first write control signals of the integrated circuit device of an embodiment include a signal applied to the gate, a signal applied to the source region, and a signal applied to the diain region to cause, piovide, produce and/or induce the first source cunent, wherein one or more of. the signal applied to the source region includes a fust voltage having a first amplitude; the signal applied to the drain region includes a second voltage having a second amplitude; and the signal applied to the gate includes a third voltage having a third amplitude and a fourth voltage having a fourth amplitude

The first write control signals of the integrated circuit device of an embodiment include a first potential difference applied between the source region and the drain region and a signal applied to the gate that includes a first voltage, wheiein the first write control signals may cause, provide, produce and/or induce an accumulation of minority carriers in the first portion of the body legion.

The minority carriers of the integrated circuit device of an embodiment accumulate at a surface region of the fust portion of body region that is juxtaposed or near a gate dielectric which is disposed between the gate and the first portion of the body region

The minority carriers of the integrated circuit device of an embodiment accumulate at a sui face region of the first portion of the body region, wherein the surface region is disconnected from the source region by the second portion of the body region.

The minority carriers of the integrated circuit device of an embodiment accumulate at a surface region of the first portion of the body region, wherein the surface region is disconnected from the drain region by the third portion of the body region. The first write control signals of the integrated circuit device of an embodiment cause, provide, produce and/oi induce source current in the body legion as a result of impact ionization induced by the minority carriers.

The signal applied to the gate of the integrated circuit device of an embodiment temporally changes to a second voltage that causes, provides, produces and/or induces an accumulation of majority carriers in the first portion of the body region, wherein the majority carriers result in the first data state.

The second wiite control signals of the integrated circuit device of an embodiment include a second potential difference applied between the source region and the drain region and a signal applied to the gate that includes the first voltage, wherein the second write

control signals prevent the first data state from being written into the first portion of the body transistor.

The second potential difference of the integrated circuit device of an embodiment is relatively less than the first potential difference. The integrated circuit device of an embodiment comprises data sense ciicuitry coupled to the memory cell and configured to sense the data state of the memory cell, wheiein, in response to read control signals applied to the memory cell, the transistor- generates a second source current which is representative of the data state of the memory cell, wherein the data sense circuitry determines the data state of the memory cell at least substantially based on the second source cuirent.

The read control signals of the integrated circuit device of an embodiment include a signal applied to the gate, source region, and drain region to cause, force and/or induce the source current which is representative of the data state of the memory cell.

The read control signals of the integrated circuit device of an embodiment include a first potential difference applied between the source region and the drain region.

The signal applied to the gate region of the integrated circuit device of an embodiment includes a negative voltage pulse.

Aspects of the present inventions described herein, and/or embodiments thereof, may include an integrated circuit device comprising one or more of: a memory cell array including one or more of a plurality of word lines, plurality of source lines, plurality of bit lines, and plurality of memory cells arranged in a matrix of rows and columns; wherein each memory cell includes a transistor comprising one or more of a body region configured to be electrically floating, a gate disposed over a first portion of the body region, the gate coupled to an associated word line, a source region adjoining a second portion of the body region, the second portion adjacent the first portion and separating the source region from the first portion, the source region coupled to an associated source line, and a drain region adjoining a third portion of the body region, the third portion adjacent the first portion and separating the drain region from the first portion, the drain region coupled to an associated bit line, wherein each memory cell includes a first data state representative of a first charge in the first portion of the body region, wherein each memory cell includes a second data state lepiesentative of a second charge in the first portion of the body region, wherein the source region of each memory cell of a first row of memoiy cells is connected to a first source line; data write circuitry coupled to the memory cells of the first row of memory cells, the data write circuitry configured to apply first write control signals to memory cells of the first row

of memoiy cells to write the first data state and second write control signals to memory cells of the first row of memory cells to write the second data state, wherein, in response to first write control signals applied to at least a portion of the memoiy cells of the first low of memory cells, the electrically floating body transistor of each memory cell of the portion of the memory cells of the first row of memory cells generates a first souice current which at least substantially provides the first charge in the first body region of the electrically floating body transistor of the portion of the memoiy cells of the fust row of memory cells.

The source region of each memory cell of a second row of memory cells of the integrated ciicuit device of an embodiment is connected to the first souice line. The integrated circuit device of an embodiment comprises one or more of: the source region of each memory cell of a second row of memoiy cells connected to a second souice line; the souice region of each memory cell of a thiid low of memory cells connected to a second source line, wherein the second and thiid rows of memory cells are adjacent to the first row of memory cells. The first write control signals of the integiated circuit device of an embodiment cause, provide, produce and/or induce the first source current.

The first write control signals of the integiated ciicuit device of an embodiment include a signal applied to the gate and a signal applied to the souice legion, wherein the signal applied to the gate includes a fust voltage having a fust amplitude and a second voltage having a second amplitude

The first write control signals of the integiated circuit device of an embodiment include a signal applied to the gate and a signal applied to the drain region, wheiein the signal applied to the gate includes a first voltage having a fust amplitude and a second voltage having a second amplitude. The first write contiol signals of the integrated ciicuit device of an embodiment include a potential difference applied between the source region and the drain region.

The first write contiol signals of the integrated circuit device of an embodiment include a signal applied to the gate, wherein the signal applied to the gate includes a fust voltage having a first amplitude and a second voltage having a second amplitude. The data write circuitry of the integrated circuit device of an embodiment, prior to applying the first write control signals, applies the second write control signals to all of the memory cells of the first row of memory cells to write the second data state therein.

The data write circuitiy of the integrated circuit device of an embodiment at least substantially simultaneously applies one or more of: the first write control signals to the

poition of the memoiy cells of the first row of memory cells to write the first data state therein; and the second write control signals to the other portion of the memoiy cells of the first row of memoiy cells to write the second data state therein.

The first write control signals of the integrated circuit device of an embodiment include a signal applied to the gate, a signal applied to the source region, and a signal applied to the diain region of one or more memory cells of the first row of memory cells to cause, provide, produce and/oi induce the first source current, wherein one or more of: the signal applied to the source region includes a first voltage having a first amplitude; the signal applied to the drain iegion includes a second voltage having a second amplitude, and the signal applied to the gate includes a third voltage having a third amplitude and a fourth voltage having a fourth amplitude.

The first write contiol signals of the integrated ciicuit device of an embodiment include a first potential difference applied between the source iegion and the drain region and a signal applied to the gate of one oi more memoiy cells of the first row of memory cells that includes a first voltage, wheiein the first wiite contiol signals may cause, piovide, produce and/or induce an accumulation of minority carriers at a suiface iegion of the first portion of the body region.

The suiface iegion of the first portion of body region of the integrated circuit device of an embodiment is juxtaposed or near a gate dielectric which is disposed between the gate and the fust poition of the body iegion

The suiface iegion of the integrated circuit device of an embodiment is disconnected from the source iegion by the second portion of the body iegion

The suiface iegion of the integrated circuit device of an embodiment is disconnected from the diain iegion by the thiid portion of the body region. The first write control signals of the integrated ciicuit device of an embodiment cause, provide, produce and/or induce souice current in the body region as a result of impact ionization induced by the minority carriers.

The signal applied to the gate of the integrated ciicuit device of an embodiment temporally changes to a second voltage that causes, ptovides, produces and/or induces an accumulation of majority carriers in the body iegion, wherein the majority carriers result in the fust data state.

The integrated ciicuit device of an embodiment comprises data sense ciicuitry coupled to each memory cell of the plurality of memory cells and configured to sense the data state of the memory cells, wheiein, in response to read control signals applied to the

memoiy cells, the transistor of each memory cell generates a second source current which is lepresentative of the data state of the memory cell, wherein the data sense circuitiy deteimines the data state of the memory cell at least substantially based on the second souice current The read control signals of the integrated circuit device of an embodiment include a signal applied to the gate, source region, and drain region to cause, force and/or induce the source curient which is representative of the data state of the memory cell.

The read control signals of the integrated circuit device of an embodiment include a first potential difference applied between the source region and the drain region The signal applied to the gate region of the integrated circuit device of an embodiment includes a negative voltage pulse.

There are many inventions described and illustrated herein. While certain embodiments, features, attributes and advantages of the inventions have been described and illustrated, it should be understood that many others, as well as different and/or similar embodiments, features, attributes and advantages of the present inventions, are apparent from the description and illustrations As such, the embodiments, features, attributes and advantages of the inventions described and illustrated herein are not exhaustive and it should be understood that such other, similar, as well as different, embodiments, features, attributes and advantages of the present inventions are within the scope of the present inventions.

As mentioned above, the illustrated/example voltage levels to implement the read and write operations are merely examples. The indicated voltage levels may be relative or absolute Alternatively, the voltages indicated may be relative in that each voltage level, for example, may be increased or decreased by a given voltage amount (for example, each voltage may be increased or decreased by 0.1, 0.15, 0.25. 0.5. 1 volt) whether one or moie of the voltages (for example, the source, drain or gate voltages) become or aie positive and negative.

The illustrated/example voltage levels and timing to implement the write and read operations are merely examples. In this regard, in certain embodiments, the contiol signals increase the potential of electrically floating body region of the transistor of the memory cell which "turns on" or produces a source current in the transistor In the context of a write operation, the source current generates majority earners in the electrically floating body region which are then stored. In the context of a read operation, the data state may be determined primarily by, sensed substantially using and/or based substantially on the source

cuπent that is responsive to the read control signals and significantly less by the interface channel cuπent component, which is less significant and/or negligible relatively to the bipolar component.

As mentioned above, each of the aspects of the piesent inventions, and/or embodiments thereof, may be employed alone or in combination with one or more of such aspects and/oi embodiments For the sake of brevity, those permutations and combinations will not be discussed separately herein As such, the present inventions are neither limited to any single aspect (nor embodiment thereof), nor to any combinations and/oi permutations of such aspects and/oi embodiments. Moieover, the above embodiments of the present inventions are merely example embodiments. They are not intended to be exhaustive oi to limit the inventions to the precise forms, techniques, materials and/oi configurations disclosed. Many modifications and variations are possible in light of the above teaching. It is to be undei stood that othei embodiments may be utilized and operational changes may be made without departing from the scope of the present inventions. As such, the foregoing description of the example embodiments of the inventions has been presented for the purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the inventions not be limited solely to the desciiption above