FILM BULK ACOUSTIC RESONATOR

摘要

A film bulk acoustic resonator comprises a substrate (12) of a single silicon crystal, a base film (13) formed on the substrate (12) and composed of a dielectric film mainly containing silicon oxide, and a piezoelectric multilayer 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 multilayer structure (14). The piezoelectric multilayer structure (14) includes a lower electrode (15), a piezoelectric film (16), and an upper electrode (17) in this order from below. The substrate (12) has a via hole 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 film bulk acoustic resonator has a large electromechanical coupling coefficient, an excellent acoustic quality factor (Q), an excellent frequency-temperature characteristic, high characteristics, and a high performance.