Filter device and multiplexer

A filter device comprising:

• a first signal terminal and a second signal terminal;
• and
• a plurality of resonators including a plurality of series arm resonators and a plurality of parallel arm resonators;
• wherein
• at least one of the plurality of series arm resonators and the plurality of parallel arm resonators is an excitation angle change resonator;
• the excitation angle change resonator includes a piezoelectric substrate including a piezoelectric body layer, and an interdigital transducer (IDT) electrode including a plurality of electrode fingers provided on the piezoelectric substrate;
• the piezoelectric body layer includes a propagation axis;
• the plurality of electrode fingers are curved;
• an excitation direction of an acoustic wave in a portion of an electrode finger in the plurality of electrode fingers is one of a first direction perpendicular or substantially perpendicular to an extending direction of the electrode finger, a second direction connecting a shortest distance between the electrode finger and an electrode finger adjacent to the electrode finger, and a third direction of an electric field vector generated between the electrode finger and the electrode finger adjacent to the electrode finger;
• when an angle between the excitation direction and an extending direction of the propagation axis is defined as an excitation angle, the excitation angle is not uniform in the IDT electrode of the excitation angle change resonator;
• when a set of the series arm resonator and the parallel arm resonator which are adjacent to each other is defined as one ladder portion, a plurality of the ladder portions are provided between the first signal terminal and the second signal terminal;
• at least one of the series arm resonator and the parallel arm resonator is a mutually different resonator in the adjacent ladder portions;
• and
• when half the ladder portions located on a first signal terminal side in all of the ladder portions are defined as front half ladder portions, and the resonators in the plurality of resonators, from the resonator located closest to the first signal terminal side to the series arm resonator and the parallel arm resonator of the ladder portion located closest to a second signal terminal side in the front half ladder portions are defined as front half resonators, at least one of the front half resonators is the excitation angle change resonator.