Acoustic wave device

An acoustic wave device comprising:

• a piezoelectric body layer including a first main surface and a second main surface opposing each other;
• a high acoustic velocity member disposed on the first main surface of the piezoelectric body layer and in which an acoustic velocity of a bulk wave propagating through the high acoustic velocity member is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric body layer;
• and
• a plurality of IDT electrodes provided on the second main surface of the piezoelectric body layer;
• wherein
• a plurality of acoustic wave resonators include the piezoelectric body layer, the high acoustic velocity member, and the plurality of IDT electrodes;
• the plurality of acoustic wave resonators include at least one series arm resonator including a first IDT electrode and at least one parallel arm resonator including a second IDT electrode;
• the first IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers interdigitating each other;
• a first envelope which is an imaginary line connecting tips of the plurality of first electrode fingers obliquely extends with respect to an acoustic wave propagation direction and a second envelope which is an imaginary line connecting tips of the plurality of second electrode fingers obliquely extends with respect to the acoustic wave propagation direction;
• the second IDT electrode includes a first busbar and a second busbar facing each other, a plurality of third electrode fingers each including an end connected to the first busbar, and a plurality of fourth electrode fingers each including an end connected to the second busbar and which are interdigitated with the plurality of third electrode fingers;
• the second IDT electrode includes an interdigitation region in which the third electrode fingers and the fourth electrode fingers overlap with each other in the acoustic wave propagation direction, and the interdigitation region includes a central region located in a central portion in a direction orthogonal or substantially orthogonal to the acoustic wave propagation direction, a first low acoustic velocity region disposed towards the first busbar relative to the central region and in which an acoustic velocity is lower than an acoustic velocity in the central region, and a second low acoustic velocity region disposed towards the second busbar relative to the central region and in which an acoustic velocity is lower than the acoustic velocity in the central region;
• and
• the second IDT electrode includes a first high acoustic velocity region disposed towards the first busbar relative to the interdigitation region in the direction orthogonal or substantially orthogonal to the acoustic wave propagation direction and in which an acoustic velocity is higher than the acoustic velocity in the central region, and a second high acoustic velocity region disposed towards the second busbar relative to the interdigitation region in the direction orthogonal or substantially orthogonal to the acoustic wave propagation direction and in which an acoustic velocity is higher than the acoustic velocity in the central region.