FILM BULK ACOUSTIC RESONATOR

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A thin film bulk acoustic resonator comprises a substrate ( 12 ) of a silicon single crystal, a base film ( 13 ) formed on the substrate ( 12 ) and composed of a dielectric film mainly containing silicon oxide, and a piezoelectric stacked structure ( 14 ) formed on the base film ( 13 ). A vibratory section ( 21 ) composed of a part of the base film ( 13 ) and a part of the piezoelectric stacked structure ( 14 ). The piezoelectric stacked structure ( 14 ) includes a lower electrode ( 15 ), a piezoelectric film ( 16 ), and an upper electrode ( 17 ) formed in this order from below. The substrate ( 12 ) had a via hole ( 20 ) in the region corresponding to the vibratory section ( 21 ). The via hole forms a space for allowing vibration of the vibratory section ( 21 ). The piezoelectric film ( 16 ) is an aluminum nitride thin film containing 0.2 to 3.0 atom % of alkaline earth metal and/or a rare earth metal. Thus, the thin film bulk acoustic resonator has a high performance such as a large electromechanical coupling coefficient, an excellent acoustic quality factor (Q) and an excellent frequency-temperature characteristic.