Acoustic wave device and acoustic wave filter device

An acoustic wave device, comprising:

• a piezoelectric layer including a first main surface and a second main surface opposite to the first main surface in a first direction;
• an interdigital transducer (IDT) electrode on at least one of the first main surface or the second main surface of the piezoelectric layer, and including a plurality of electrode fingers arranged in an arrangement direction;
• a support facing the second main surface of the piezoelectric layer, and including an acoustic reflection portion at a portion closer to the second main surface of the piezoelectric layer;
• and
• a load film extending over a region that overlaps, when viewed in plan in the first direction, at least electrode fingers from a fourth electrode finger of the plurality of electrode fingers from a first outer end in the arrangement direction to a fourth electrode finger of the plurality of electrode fingers from a second outer end in the arrangement direction;
• wherein
• the load film is not located over at least a portion of a region that overlaps, in a plan view, a first electrode finger of the plurality of electrode fingers located outermost in the arrangement direction;
• and
• d/p is less than or equal to about 0.5, where d denotes a thickness of the piezoelectric layer, and p denotes a center-to-center distance between adjacent two of the electrode fingers.