Acoustic wave device, filter, and multiplexer

An acoustic wave device comprising:

• a piezoelectric body;
• a pair of comb-shaped electrodes provided on the piezoelectric body, the pair of comb-shaped electrodes including a plurality of electrode fingers;
• a reflector provided on the piezoelectric body so as to be arranged in line with the pair of comb-shaped electrodes in an arrangement direction of the plurality of electrode fingers;
• and
• an additional film that is provided on the piezoelectric body between the pair of comb-shaped electrodes and the reflector so that an overlap width with the pair of comb-shaped electrodes and an overlap width with the reflector are equal to or less than ⅛ of an average pitch of the plurality of electrode fingers of the pair of comb-shaped electrodes and a distance between the additional film and the pair of comb-shaped electrodes and a distance between the additional film and the reflector are equal to or less than ⅛ of the average pitch,
• wherein a value obtained by multiplying a thickness of the additional film by a density of the additional film is equal to or greater than 0.4 times and equal to or less than 1.6 times a value obtained by multiplying the thickness of the plurality of electrode fingers by a duty ratio of the plurality of electrode fingers and a density of the plurality of electrode fingers.

An acoustic wave device comprising:

• a piezoelectric body including a first section having a first thickness and a second section having a second thickness less than the first thickness;
• a pair of comb-shaped electrodes provided on the piezoelectric body, the pair of comb-shaped electrodes including a plurality of electrode fingers;
• and
• a reflector provided on the piezoelectric body, the reflector being provided in line with the pair of comb-shaped electrodes in an arrangement direction of the plurality of electrode fingers, wherein the pair of comb-shaped electrodes and the reflector are provided in the first section of the piezoelectric body, and
• wherein a section of the piezoelectric body between the pair of comb-shaped electrodes and the reflector is the second section.