Patent ID: 8723623

Claim:
An acoustic wave device comprising: a substrate; and a plurality of piezoelectric thin film resonators formed over the substrate, each of the plurality of the piezoelectric thin film resonators including, a lower electrode provided on the substrate, a piezoelectric film provided on the lower electrode, and an upper electrode provided on the piezoelectric film and opposed to the lower electrode through the piezoelectric film, each of the piezoelectric thin film resonators being partly supported by the substrate and extending above the substrate to form a cavity between the substrate and the lower electrode, the cavity being continuously extended under at least two of the plurality of the piezoelectric thin film resonators so as to be shared by said at least two of the plurality of the piezoelectric thin film resonators, wherein a through hole is formed to extend from an upper surface of the piezoelectric thin film resonators and penetrate the lower electrode of at least one of said at least two of the plurality of piezoelectric thin film resonators sharing the cavity, the through hole being positioned away from peripheral edges of the cavity and the upper electrode as viewed in a plan view, wherein said at least two of the plurality of the piezoelectric thin film resonators that share the cavity include at least one series resonator and at least one parallel resonator that form a ladder type filter, wherein a plurality of said cavities are provided, and each of the plurality of the cavities is shared by a different set of the at least two of the plurality of piezoelectric thin film resonators, and wherein for each cavity, the number of the through hole is less than the number of the resonators that form the ladder type filter.