THIN FILM PIEZOELECTRIC RESONATOR AND THIN FILM PIEZOELECTRIC FILTER USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a thin film piezoelectric resonator having a high Q value in which generation of a transverse acoustic mode is suppressed.;SOLUTION: The thin film piezoelectric resonator includes: a piezoelectric resonance stack 12 having a piezoelectric layer 2 and an upper electrode 10 and a lower electrode 8 formed so as to be opposite to each other on both sides of the piezoelectric layer 2; a gap 4 formed under the piezoelectric resonance stack 12; and a substrate 6 supporting the piezoelectric resonance stack 12. The piezoelectric resonance stack 12 is comprised of: an oscillation area 18 in which the upper electrode 10 and the lower electrode 8 are opposite to each other via a piezoelectric layer 2 and located in accordance with the gap 4; a supporting area 22 which contacts the substrate; and a buffer area 20 located between the oscillation area 18 and the support area 22. The buffer area 20 is constituted so that a resonance frequency of primary thickness longitudinal vibration becomes lower than in the oscillation area 18. The piezoelectric layer 2 is comprised of materials indicating a dispersion curve of a high-frequency cutoff type. The buffer area 20 includes the oscillation area 18.;COPYRIGHT: (C)2008,JPO&INPIT