Acoustic wave device

An acoustic wave device comprising:

• a piezoelectric substrate that is a laminate including a support including a support substrate and a piezoelectric layer on the support;
• and
• an IDT electrode on the piezoelectric layer and including paired busbars and a plurality of electrode fingers;
• wherein
• in the IDT electrode, as viewed from an acoustic wave propagation direction, a region where the electrode fingers adjacent to each other overlap each other is an intersection region, regions between the intersection region and the paired busbars are paired gap regions, when a direction in which the plurality of electrode fingers extends is defined as an electrode finger extending direction, the paired gap regions include respective gap portions located on an extension line in the electrode finger extending direction of the plurality of electrode fingers;
• a through-hole is provided in a portion of the piezoelectric layer overlapping at least one of the gap portions in plan view;
• a hollow portion is provided in a portion of the support overlapping the through-hole in plan view, the hollow portion extends farther toward a center side of the IDT electrode in the electrode finger extending direction than the portion provided with the through-hole;
• one or more layers other than the piezoelectric layer in the piezoelectric substrate are constraining layers that constrain the piezoelectric layer at a portion overlapping the intersection region in plan view, and the piezoelectric layer includes a protruding portion protruding farther in the electrode finger extending direction than at least one layer of the constraining layers.