To easily realize impedance matching between an electrode and a piezoelectric film in a bulk acoustic wave resonator in which a lower electrode, a piezoelectric film, and an upper electrode are formed on a substrate and a PZT having a high mechanical coupling efficiency is used for the piezoelectric film to increase a pass band.
A through-hole wiring 17 used as a lead-out electrode to the outside is formed on a substrate 12, and the lower electrode 20 is formed thereon, and then, the PZT film 21 and the upper electrode 22 are formed. Accordingly, before the PZT film 21 is formed without causing damage on the PZT film 21, the through-hole wiring 17 and the lower electrode 20 are formed by an arbitrary method capable of easily obtaining dimension accuracy and impedance can be highly accurately controlled, and the impedance matching can be easily realized between the electrodes 20, 22 and the PZT film 21. Further, since the necessity of routing the lower electrode 20 can be eliminated, a dual layer of the lower electrode and the upper electrode is not required on the routing portion in a conventional technique, an element area can be reduced.
COPYRIGHT: (C)2008,JPO&INPIT
SI-BEI XIONG
SHIRAI TAKEO
HAYAZAKI YOSHIKI
MATSUSHIMA CHOMEI
Takao Ito
Jiro Higuchi