Patent ID: 9748925
Date: 2017-08-29
CPC Classifications: H03H

Claim:
1. A piezoelectric thin film resonator comprising: a substrate; a piezoelectric film located on the substrate; a lower electrode and an upper electrode facing each other across at least a part of the piezoelectric film; and an insertion film inserted in the piezoelectric film, located in at least a part of an outer peripheral region within a resonance region, and not located in a center region of the resonance region, the resonance region being a region where the lower electrode and the upper electrode face each other across the piezoelectric film, wherein a difference between a total film thickness of the piezoelectric film and the insertion film in a first region within the resonance region and a film thickness of the piezoelectric film in a second region is less than a film thickness of the insertion film, the first region being a region in which the insertion film is inserted, and the second region being a region in which the insertion film is not inserted, and wherein: the piezoelectric film includes a lower piezoelectric film and an upper piezoelectric film located on the lower piezoelectric film, a recessed portion is formed in an upper surface of the lower piezoelectric film so that the first region corresponds to a bottom of the recessed portion, and the insertion film is located on a bottom surface of the recessed portion.