Acoustic wave device, filter, and multiplexer

An acoustic wave device comprising:

• a support substrate;
• a piezoelectric layer provided over the support substrate;
• at least one pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the at least one pair of comb-shaped electrodes including electrode fingers;
• a temperature compensation film interposed between the support substrate and the piezoelectric layer, the temperature compensation film having a temperature coefficient of elastic constant opposite in sign to a temperature coefficient of elastic constant of the piezoelectric layer;
• and
• an insulating layer interposed between the support substrate and the temperature compensation film, a first surface of the insulating layer having a plurality of first protruding portions and/or a plurality of first recessed portions, a second surface of the insulating layer having a plurality of second protruding portions and/or a plurality of second recessed portions, the first surface being closer to the support substrate, the second surface being closer to the temperature compensation film,
• wherein the plurality of first protruding portions and/or the plurality of first recessed portions are arranged at regular intervals, and the plurality of second protruding portions and/or the plurality of second recessed portions are arranged at regular intervals,
• wherein the regular intervals at which the plurality of first protruding portions and/or the plurality of first recessed portions are arranged are substantially equal to the regular intervals at which the plurality of second protruding portions and/or the plurality of second recessed portions are arranged, and
• wherein the regular intervals at which the plurality of first protruding portions and/or the plurality of first recessed portions are arranged and the regular intervals at which the plurality of second protruding portions and/or the plurality of second recessed portions are arranged are equal to or greater than 1.6 times an average pitch of the electrode fingers.

An acoustic wave device comprising:

• a support substrate;
• a piezoelectric layer provided over the support substrate;
• at least one pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the at least one pair of comb-shaped electrodes including electrode fingers;
• a temperature compensation film interposed between the support substrate and the piezoelectric layer, the temperature compensation film having a temperature coefficient of elastic constant opposite in sign to a temperature coefficient of elastic constant of the piezoelectric layer;
• and
• an insulating layer interposed between the support substrate and the temperature compensation film, a first surface of the insulating layer having a plurality of first protruding portions and/or a plurality of first recessed portions, a second surface of the insulating layer having a plurality of second protruding portions and/or a plurality of second recessed portions, the first surface being closer to the support substrate, the second surface being closer to the temperature compensation film,
• wherein an arithmetic average roughness Ra of the second surface is 1 nm or less.