Acoustic wave device and acoustic wave filter device

An acoustic wave device comprising:

• a piezoelectric layer including a first major surface and a second major surface opposite the first major surface in a first direction;
• an interdigital transducer (IDT) electrode on at least one of the first major surface or the second major surface of the piezoelectric layer, and including a plurality of electrode fingers arranged in an arrangement direction;
• a support facing the second major surface of the piezoelectric layer, and including an acoustic reflection portion on a side facing the second major surface of the piezoelectric layer;
• and
• an additional electrode in a region overlying at least one of a first electrode finger or a second electrode finger, the first electrode finger being an electrode finger among the plurality of electrode fingers located at an outermost position in the arrangement direction, and the second electrode finger being an electrode finger adjacent to the first electrode finger among the plurality of electrode fingers;
• wherein
• a sum of a product of a width, a height, and a density of at least one of the first electrode finger or the second electrode finger and a product of a width, a height, and a density of the additional electrode is greater than a product of a width, a height, and a density of a central electrode finger different from the first electrode finger and the second electrode finger among the plurality of electrode fingers;
• and
• when a thickness of the piezoelectric layer is denoted by d and a center-to-center distance between adjacent electrode fingers among the plurality of electrode fingers is denoted by p, d/p is less than or equal to about 0.5.