Piezoelectric resonator, filter, resonance frequency adjustment method of the duplexer and the piezoelectric resonator

摘要

PROBLEM TO BE SOLVED: To make adjustable easily the resonant frequency of a piezoelectric resonator. SOLUTION: The piezoelectric resonator 1 has a substrate 11, a lower barrier layer 12 provided below the substrate 11, an upper barrier layer 13 provided on the substrate 11, a lower electrode 14 provided on the upper barrier layer 13, a piezoelectric thin film 15 provided on the lower electrode 14, and an upper electrode 16 provided on the piezoelectric thin film 15. Furthermore, the piezoelectric resonator 1 has an impedance-adjusting portion 20 provided on the piezoelectric thin film 15, connected with the upper electrode 16, has a grounding electrode 17 provided under the lower barrier layer 12, and is provided at a position facing the impedance-adjusting portion 20. The impedance-adjusting portion 20 includes one or more cutting planned portions, capable of being cut to vary its impedance, corresponding to the states of the cuttingly predetermined portions. By selecting the states of the impedance-adjusting portion 20, the resonant frequency of the piezoelectric resonator 1 is adjusted.