Patent ID: 11996828

Abstract:
A filter device includes a piezoelectric substrate including a high acoustic velocity material layer and a piezoelectric layer, and series and parallel arm resonators on the piezoelectric substrate. The parallel arm resonator includes a first IDT electrode on the piezoelectric substrate, and the series arm resonator includes a second IDT electrode on the piezoelectric substrate. First and second busbars of the first IDT electrode include opening formation regions, and an occupancy ratio of areas of openings in the first and second busbars of the first IDT electrode is greater than an occupancy ratio of areas of openings in first and second busbars of the second IDT electrode. In the first and second IDT electrodes, low acoustic velocity regions sandwich a central region. A high acoustic velocity region is provided in the opening formation region of each of the first and second busbars in the first IDT electrode.