Patent ID: 8653908

Claim:
A piezoelectric thin film resonator, comprising: a substrate, an intermediate layer disposed on the substrate and formed of an insulator, a lower electrode disposed on the intermediate layer, a piezoelectric film disposed on the lower electrode, and an upper electrode disposed at a portion facing the lower electrode with the piezoelectric film interposed therebetween, wherein in a resonance region where the lower electrode and the upper electrode face each other, a space is provided below the lower electrode so as to promote piezoelectric resonance, wherein the resonance region and a region of the space cross each other, wherein in the resonance region, all or part of an intermediate region that is a region of the resonance region excluding the region of the space is fixed to the intermediate layer, and wherein the thickness of the intermediate layer is 0.10 to 0.30 times a wavelength of an elastic wave which spreads in a thickness direction in the intermediate layer at an anti-resonance frequency of the piezoelectric thin film resonator.