PURPOSE: To improve the surge breakdown strength of a low voltage Zener diode and to lower the leak current value corresponding to the breakdown voltage by forming a region of the same conductivity as the main body and high in impurity concentration on the semiconductor body side of a pn junction face, and forming a guard ring deeper than at least the sum of the depths of both regions, surrounding both of them.
CONSTITUTION: On the whole face of the N-type epitaxial layer 2 at the surface of an N-type semiconductor an N+-type diffusion layer 3 higher in impurity concentration than this is formed in depth k. The oxide film 4 on that is etched selectively to form a contact hole 7a, and boron (p-type impurities) are implanted circularily in depth l deeper than the depth k of the diffusion layer 3 so as to form a guard ring 5. Next, boron(B) is implanted in shallower depth m than depth k and in fixed concentration into the part 3a surrounded by this so as to form a P-type diffusion layer 6 being the same conductivity type as the guard ring 5. After that, additional diffusion is applied so that Zener voltage Vz may be nearly the desired value, and an electrode 7 is filled in a contact hole 7a, and is brought into contact with the diffusion layer 6, thus a constant voltage Zener diode 10 is obtained.
| JP5206259 | Semiconductor device |
| JP5271694 | diode |
| WO/2007/135146 | SEMICONDUCTOR COMPONENT AND RECTIFIER ARRANGEMENT |
SAEGUSA KUNIHIRO
SATO TAKASHI
HITACHI TOKYO ELECTRONICS