Acoustic wave element, acoustic wave filter device, and multiplexer

An acoustic wave element comprising:

• a piezoelectric substrate;
• an interdigital transducer (IDT) electrode on the piezoelectric substrate and including a pair of comb-shaped electrodes that oppose each other;
• and
• a reflector located adjacent to the IDT electrode;
• wherein
• each comb-shaped electrode defining the pair of comb-shaped electrodes includes a plurality of comb electrode fingers extending in a first direction;
• the reflector includes a plurality of reflective electrode fingers extending in the first direction, and is located adjacent to the IDT electrode in a second direction that intersects with the first direction;
• in a boundary region between the IDT electrode and the reflector, a distance in the second direction between a center of a comb electrode finger closest to the reflector among the plurality of comb electrode fingers and a center of a reflective electrode finger closest to the IDT electrode among the plurality of reflective electrode fingers is set as an IDT-reflector gap;
• an inter-center distance in the second direction between electrode fingers adjacent to each other in the second direction among the electrode fingers of each of the plurality of comb electrode fingers and the plurality of reflective electrode fingers is set as a pitch;
• the comb electrode finger closest to the reflector among the plurality of comb electrode fingers is set as a first end-side electrode finger;
• the comb electrode fingers in a direction from the first end-side electrode finger toward a center of the IDT electrode are sequentially set as an n-th end-side electrode finger (n is a natural number);
• a pitch between the n-th end-side electrode finger and an (n+1)-th end-side electrode finger is set as an n-th end-side pitch;
• an average value of each pitch by all of the comb electrode fingers included in the IDT electrode is set as an average IDT pitch;
• an average value of each pitch by all of the reflective electrode fingers included in the reflector is set as an average reflector pitch;
• a ratio of the n-th end-side pitch to the average IDT pitch is set as a variable represented by x;
• a ratio of the IDT-reflector gap to the average reflector pitch is set as a variable represented by y;
• n of the n-th end-side electrode finger is equal to or more than 6 and equal to or less than 10;
• and
• each of the ratio of the n-th end-side pitch and the ratio of the IDT-reflector gap is a value in a region surrounded by a curve defined by (Formula 1) and a curve defined by (Formula 2)
• y=(59.084x3−148.85x2+122.38x−32.175)×2 (Formula 1)
• y=(73.168x3−193.95x2+168.75x−47.552)×2 (Formula 2).

An acoustic wave element comprising:

• a piezoelectric substrate;
• an interdigital transducer (IDT) electrode on the piezoelectric substrate and including a pair of comb-shaped electrodes that oppose each other;
• and
• a reflector located adjacent to the IDT electrode;
• wherein
• each comb-shaped electrode defining the pair of comb-shaped electrodes includes a plurality of comb electrode fingers extending in a first direction;
• the reflector includes a plurality of reflective electrode fingers extending in the first direction, and is located adjacent to the IDT electrode in a second direction that intersects with the first direction;
• in a boundary region between the IDT electrode and the reflector, a distance in the second direction between a center of a comb electrode finger closest to the reflector among the plurality of comb electrode fingers and a center of a reflective electrode finger closest to the IDT electrode among the plurality of reflective electrode fingers is set as an IDT-reflector gap;
• an inter-center distance in the second direction between electrode fingers adjacent to each other in the second direction among the electrode fingers of each of the plurality of comb electrode fingers and the plurality of reflective electrode fingers is set as a pitch;
• the comb electrode finger closest to the reflector among the plurality of comb electrode fingers is set as a first end-side electrode finger;
• the comb electrode fingers in a direction from the first end-side electrode finger toward a center of the IDT electrode are sequentially set as an n-th end-side electrode finger (n is a natural number);
• a pitch between the n-th end-side electrode finger and an (n+1)-th end-side electrode finger is set as an n-th end-side pitch;
• an average value of each pitch by all of the comb electrode fingers included in the IDT electrode is set as an average IDT pitch;
• an average value of each pitch by all of the reflective electrode fingers included in the reflector is set as an average reflector pitch;
• a ratio of the n-th end-side pitch to the average IDT pitch is set as a variable represented by x;
• a ratio of the IDT-reflector gap to the average reflector pitch is set as a variable represented by y;
• n of the n-th end-side electrode finger is equal to or more than 5 and equal to or less than 11;
• and
• each of the ratio of the n-th end-side pitch and the ratio of the IDT-reflector gap is a value in a region surrounded by a curve defined by (Formula 1) and a curve defined by (Formula 2)
• y=(59.084x3−148.85x2+122.38x−32.175)×2 (Formula 1)
• y=(73.168x3−193.95x2+168.75x−47.552)×2 (Formula 2).

An acoustic wave element comprising:

• a piezoelectric substrate;
• an interdigital transducer (IDT) electrode on the piezoelectric substrate and including a pair of comb-shaped electrodes that oppose each other;
• and
• a reflector located adjacent to the IDT electrode in an acoustic wave propagation direction;
• wherein
• each comb-shaped electrode defining the pair of comb-shaped electrodes includes a plurality of comb electrode fingers extending in a direction that intersects with the acoustic wave propagation direction;
• the reflector includes a plurality of reflective electrode fingers extending in the direction that intersects with the acoustic wave propagation direction;
• in a boundary region between the IDT electrode and the reflector, a distance in the acoustic wave propagation direction between a center of a comb electrode finger closest to the reflector among the plurality of comb electrode fingers and a center of a reflective electrode finger closest to the IDT electrode among the plurality of reflective electrode fingers is set as an IDT-reflector gap;
• an inter-center distance in the acoustic wave propagation direction between electrode fingers adjacent to each other in the acoustic wave propagation direction among the electrode fingers of each of the plurality of comb electrode fingers and the plurality of reflective electrode fingers is set as a pitch;
• the comb electrode finger closest to the reflector among the plurality of comb electrode fingers is set as a first end-side electrode finger;
• the comb electrode fingers in a direction from the first end-side electrode finger toward a center of the IDT electrode are sequentially set as an n-th end-side electrode finger (n is a natural number);
• a pitch between the n-th end-side electrode finger and an (n+1)-th end-side electrode finger is set as an n-th end-side pitch;
• an average value of each pitch by all of the comb electrode fingers included in the IDT electrode is set as an average IDT pitch;
• an average value of each pitch by all of the reflective electrode fingers included in the reflector is set as an average reflector pitch;
• a ratio of the n-th end-side pitch to the average IDT pitch is set as a variable represented by x;
• a ratio of the IDT-reflector gap to the average reflector pitch is set as a variable represented by y;
• n of the n-th end-side electrode finger is equal to or more than 5 and equal to or less than 11;
• and
• each of the ratio of the n-th end-side pitch and the ratio of the IDT-reflector gap is a value in a region surrounded by a curve defined by (Formula 1) and a curve defined by (Formula 2)
• y=(59.084x3−148.85x2+122.38x−32.175)×2 (Formula 1)
• y=(73.168x3−193.95x2+168.75x−47.552)×2 (Formula 2).