Acoustic wave resonator, filter, and duplexer

An acoustic wave resonator comprising:

• a piezoelectric substrate;
• and
• an Interdigital Transducer (IDT) that is located on the piezoelectric substrate, and includes a pair of comb-shaped electrodes facing each other, each of the pair of comb-shaped electrodes including a grating electrode that excites an acoustic wave and a bus bar to which the grating electrode is connected,
• wherein an anisotropy coefficient in an overlap region, in which the grating electrodes of the pair of comb-shaped electrodes overlap, is positive;
• an anisotropy coefficient in a region that is in the bus bar of one of the pair of comb-shaped electrodes and adjacent to a side, which is closer to the overlap region, of the bus bar of the one of the pair of comb-shaped electrodes is less than the anisotropy coefficient in the overlap region and an anisotropy coefficient in a gap region that is located between a tip of the grating electrode of another one of the pair of comb-shaped electrodes and the bus bar of the one of the pair of comb-shaped electrodes, and
• an acoustic velocity of an acoustic wave propagating through the gap region and an acoustic velocity of an acoustic wave propagating through the region that is in the bus bar of the one of the pair of comb-shaped electrodes and adjacent to the side, which is closer to the overlap region, of the bus bar of the one of the pair of comb-shaped electrodes are less than an acoustic velocity of an acoustic wave propagating through the overlap region at an antiresonant frequency.

An acoustic wave resonator comprising:

• a piezoelectric substrate;
• and
• an Interdigital Transducer (IDT) that is located on the piezoelectric substrate, and includes a pair of comb-shaped electrodes, each of the pair of comb-shaped electrodes including a grating electrode that excites an acoustic wave and a bus bar to which the grating electrode is connected,
• wherein an anisotropy coefficient in an overlap region, in which the grating electrodes of the pair of comb-shaped electrodes overlap, is positive,
• an anisotropy coefficient in a gap region is less than the anisotropy coefficient in the overlap region, the gap region being located between a tip of the grating electrode of one of the pair of comb-shaped electrodes and the bus bar of another one of the pair of comb-shaped electrodes,
• an acoustic velocity of an acoustic wave propagating through the gap region is greater than an acoustic velocity of an acoustic wave propagating through a central region of the overlap region, the central region being a region other than an edge region adjacent to the gap region in the overlap region, and
• an acoustic velocity of an acoustic wave propagating through the edge region is less than the acoustic velocity of the acoustic wave propagating through the central region.