Patent ID: 9444429
Filing Date: 2016-09-13
CPC Classification: C23C,H03H,Y10T

Claim Text:
1. A piezoelectric thin-film resonator comprising: a substrate; a piezoelectric film having a lower piezoelectric film provided on the substrate and an upper piezoelectric film provided on the lower piezoelectric film; a lower electrode and an upper electrode that face each other through at least a part of the piezoelectric film; an interposed film that is interposed between the lower piezoelectric film and the upper piezoelectric film and is located in an outer circumferential part of a resonance region in which the lower electrode and the upper electrode face each other through the piezoelectric film, while the interposed film is not provided in a central part of the resonance region; an upper surface of the lower piezoelectric film having a first roughness in a region in which the interposed film is not provided and a second roughness in another region in which the interposed film is provided, the first roughness being smaller than the second roughness.