Acoustic wave resonator, filter, and duplexer

An acoustic wave resonator comprising:

• a piezoelectric substrate;
• a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the pair of comb-shaped electrodes including a plurality of electrode fingers exciting an acoustic wave and a bus bar electrode to which the plurality of electrode fingers are connected, the pair of comb-shaped electrodes forming an overlap region in which the plurality of electrode fingers of one of the pair of comb-shaped electrodes and the plurality of electrode fingers of another of the pair of comb-shaped electrodes overlap,
• wherein each of the plurality of electrode fingers overlapping in the pair of comb-shaped electrodes includes:
• a first region that is located in the overlap region, in which a velocity of the acoustic wave is a first velocity, and of which a position in a first direction in which the plurality of electrode fingers extend changes with respect to a second direction intersecting the first direction;
• second regions that are located in the overlap region, in which a velocity of the acoustic wave is a second velocity different from the first velocity, and that sandwich the first region in the first direction;
• and
• wherein the pair of comb-shaped electrodes includes, in the plurality of electrode fingers in the overlap region, a plurality of the first regions located away from each other in the first direction, the second regions sandwiching the plurality of the first regions in the first direction, and a third region that is located between the plurality of the first regions and in which a velocity of the acoustic wave is a third velocity different from the first velocity and the second velocity.

A duplexer comprising:

• a transmit filter;
• and
• a receive filter,
• wherein at least one of the transmit filter or the receive filter is a filter including an acoustic wave resonator, and
• the acoustic wave resonator includes:
• a piezoelectric substrate;
• a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the pair of comb-shaped electrodes including a plurality of electrode fingers exciting a surface acoustic wave and a bus bar electrode to which the plurality of electrode fingers are connected, the plurality of electrode fingers having the same length, the pair of comb-shaped electrodes forming an overlap region in which the plurality of electrode fingers of one of the pair of comb-shaped electrodes and the plurality of electrode fingers of another of the pair of comb-shaped electrodes overlap,
• wherein each of the plurality of electrode fingers overlapping in the pair of comb-shaped electrodes includes:
• a first region that is located in the overlap region, in which a velocity of the surface acoustic wave is a first velocity, and of which a position in a first direction in which the plurality of electrode fingers extend changes with respect to a second direction intersecting the first direction;
• and
• second regions that are located in the overlap region, in which a velocity of the surface acoustic wave is a second velocity different from the first velocity, and that sandwich the first region in the first direction,
• wherein a length of at least one of the second regions in the first direction is longer than a length of the first region in the first direction.