Acoustic wave device

An acoustic wave device comprising:

• a support substrate having a thickness in a first direction;
• a piezoelectric layer on the support substrate;
• and
• an interdigital transducer electrode on the piezoelectric layer and including a plurality of first electrode fingers and a plurality of second electrode fingers, the plurality of first electrode fingers extending in a second direction crossing the first direction, the plurality of second electrode fingers extending in the second direction and facing corresponding ones of the plurality of first electrode fingers in a third direction orthogonal or substantially orthogonal to the second direction;
• wherein
• the support substrate and the piezoelectric layer include a hollow therebetween at a position at least partially overlapping the interdigital transducer electrode in the first direction;
• at least one through hole penetrating the piezoelectric layer at a position not overlapping the interdigital transducer electrode in the first direction, and the through hole communicates with the hollow;
• and
• a reinforcing rib not overlapping the plurality of first and second electrode fingers in the first direction is provided;
• and
• the reinforcing rib protrudes from a lateral wall of the hollow toward an interior of the hollow.