Patent ID: 8610516

Claim:
A piezoelectric thin-film filter comprising: a substrate; at least two pairs of electrodes arranged on a main surface of the substrate; and a piezoelectric thin-film disposed between the at least two pairs of electrodes; wherein at least one first resonator includes a first vibration portion defined by a first portion of the piezoelectric thin-film disposed between a first pair of the at least two pairs of electrodes and being acoustically isolated from the substrate and at least one second resonator includes a second vibration portion defined by a second portion of the piezoelectric thin-film disposed between a second pair of the at least two pairs of electrodes and being acoustically isolated from the substrate; the at least one first resonator includes an additional film that is disposed outside one of the electrodes of the first pair of electrodes constituting about half or more of an overall length of a perimeter of the first vibration portion that is in contact with the one of the electrodes when seen from a thickness direction thereof, and an external shape of the second vibration portion of the at least one second resonator, when seen from a thickness direction thereof, is a polygon and each side of the polygon is not parallel with any of the other sides of the polygon; the piezoelectric thin-film filter includes at least two series resonators defined by at least one of the at least one first resonator and at least one of the at least one second resonator; and the at least one second resonator does not include the additional film.