Elastic wave filter device, multiplexer and composite filter device

摘要

Provided is an elastic wave filter device in which deterioration of filter characteristics due to a transverse mode ripple hardly occurs. At least one series arm resonator S1, S2 and parallel arm resonators P1, P2, wherein the series arm resonators S1, S2 and the parallel arm resonators P1, P2 are made of elastic wave resonators, and at least one series arm resonator is provided. The IDT electrodes of the resonators S1 and S2 are apodized IDT electrodes with cross-width weighting. In the IDT electrodes of the parallel arm resonators P1 and P2, the intersecting portions are formed in the central region and both outsides of the central region. Having a low sound speed region provided, the sound speed of the elastic wave in the low sound speed region is lower than the sound speed of the elastic wave in the central region, and the sound wave of the elastic wave is lower outside the low sound speed region than in the low sound speed region. An acoustic wave filter device 1 provided with a high sound speed region having a high sound speed.