Acoustic wave device, radio-frequency front-end circuit, and communication apparatus

An acoustic wave device comprising:

• a piezoelectric substance;
• and
• an IDT electrode provided on the piezoelectric substance;
• wherein
• the IDT electrode includes:
• a first busbar and a second busbar facing each other;
• a plurality of first electrode fingers including first ends are connected to the first busbar;
• a plurality of second electrode fingers including first ends are connected to the second busbar, the plurality of second electrode fingers being interdigitated with the plurality of first electrode fingers;
• a crossing area where the first electrode fingers and the second electrode fingers overlap each other in an acoustic wave propagating direction;
• a first high-acoustic-velocity area;
• a second high-acoustic-velocity area;
• the crossing area includes:
• a central area positioned on a center side in a direction perpendicular or substantially perpendicular to the acoustic wave propagating direction;
• and
• a first low-acoustic-velocity area and a second low-acoustic-velocity area arranged on both sides in a direction perpendicular or substantially perpendicular to the acoustic wave propagating direction of the central area, the first low-acoustic-velocity area and the second low-acoustic-velocity area having an acoustic velocity slower than that of the central area;
• the first high-acoustic-velocity area is an area between the first busbar and the first low-acoustic-velocity area and has an acoustic velocity faster than that of the central area;
• the second high-acoustic-velocity area is an area between the second busbar and the second low-acoustic-velocity area and has an acoustic velocity faster than that of the central area;
• mass adding films are provided in respective portions of the plurality of first electrode fingers and the plurality of second electrode fingers in the first low-acoustic-velocity area and the second low-acoustic-velocity area;
• assuming that a direction in which each of the first electrode fingers extends is each first length direction and a direction in which each of the second electrode fingers extends is each second length direction, each of the mass adding films incudes a central portion positioned at a center in the each first length direction or the each second length direction, a first end portion and a second end portion positioned at both ends in the each first length direction or the each second length direction, a first end surface that is an end surface positioned in the first end portion, and a second end surface that is an end surface positioned in the second end portion;
• and
• the first end surface and the second end surface of at least one of the mass adding films are inclined with respect to a thickness direction of the mass adding films, and the at least one of the mass adding films includes a protruding portion that protrudes from at least one of the first end portion and the second end portion to a side opposite to the piezoelectric substance side.