| 摘要 |
<p>PROBLEM TO BE SOLVED: To widen the range in which a resonant frequency can be adjusted.SOLUTION: An acoustic wave device is disclosed which comprises a ladder-type filter or a lattice-type filter including a serial resonator and a parallel resonator. In the acoustic wave device, both the serial resonator and the parallel resonator are piezoelectric thin film resonators each comprising: a substrate 10; a piezoelectric thin film 14 provided on the substrate; a lower electrode 12 and an upper electrode 16 which are provided with at least a part of the piezoelectric thin film interposed therebetween; a resonance region 50 in which the lower electrode and the upper electrode oppose each other with the piezoelectric thin film interposed therebetween; and at least two layers of first additional films 28a, 28b which are provided in at least two resonance regions between the piezoelectric thin film and the lower electrode, between the piezoelectric thin film and the upper electrode, between a plurality of layers within the lower electrode, between a plurality of layers within the upper electrode, on the upper electrode, under the lower electrode, or on an insulation film provided on the upper electrode, and which are formed differently from the resonance regions, respectively. The parallel resonator includes a second additional film 20 in the resonance region.</p> |
