PIEZOELECTRIC THIN FILM RESONATOR, MANUFACTURING METHOD THEREOF, FILTER AND DUPLEXER

摘要

PROBLEM TO BE SOLVED: To improve a Q factor of a piezoelectric thin film resonator and to improve orientation of a piezoelectric film.SOLUTION: The piezoelectric thin film resonator includes: a substrate 10; a piezoelectric film 14 including a lower piezoelectric film 14a provided on the substrate and an upper piezoelectric film 14b formed on the lower piezoelectric film; lower and upper electrodes 16 which oppose each other while interposing at least a part of the piezoelectric film therebetween; and an insertion film 28 which is inserted between the lower piezoelectric film and the upper piezoelectric film, and provided in an outer peripheral area 52 within a resonance area 50 where the lower electrode and the upper electrode oppose each other while interposing the piezoelectric film therebetween, but is not provided in a central area 54 of the resonance area. Roughness on a top face of the lower piezoelectric film in the area where the insertion film is not formed is smaller than roughness on the top face of the lower piezoelectric film in the area where the insertion film is formed.