Acoustic wave element and acoustic wave device using same

An acoustic wave element, comprising:

• a piezoelectric substrate and
• an IDT electrode located on an upper surface of the piezoelectric substrate,
• wherein
• the IDT electrode comprises
• a first bus bar and a second bus bar which face each other in a direction intersecting with a propagation direction of the acoustic wave,
• a plurality of first electrode fingers which extend from the first bus bar to the second bus bar side,
• a plurality of second electrode fingers which
• extend from the second bus bar to the first bus bar side and
• have a portion adjacent to the plurality of first electrode fingers in the propagation direction,
• a plurality of first dummy electrodes which
• extend from the first bus bar to the second bus bar side and
• have tips which face the tips of the plurality of second electrode fingers through a plurality of first gaps,
• a plurality of second dummy electrodes which
• extend from the second bus bar to the first bus bar side and
• have tips which face the tips of the plurality of first electrode fingers through a plurality of second gaps,
• a first additional electrode which
• is located between a first electrode finger and a first dummy electrode which are adjacent to each other and at a position which it closes at least a portion of a first gap when viewed in the propagation direction and
• is connected to at least one of the first electrode finger or the first dummy electrode, and
• a second additional electrode which
• is located between a second electrode finger and a second dummy electrode which are adjacent to each other and at a position which it closes at least a portion of the second gaps when viewed in the propagation direction and
• is connected to at least one of the second electrode finger or the second dummy electrode, and,
• in a certain range of the propagation direction of the IDT electrode,
• when the arrangement direction of the first gaps among the plurality of first gaps which are adjacent to each other is a third direction, the third direction is inclined relative to the propagation direction,
• when the arrangement direction of the second gaps among the plurality of second gaps which are adjacent to each other is a fourth direction, the fourth direction is inclined to the side the same as the side to which the third direction is inclined relative to the propagation direction, and
• when the inclination angle of the third direction relative to the propagation direction is a third angle θC and the inclination angle of the fourth direction relative to the propagation direction is a fourth angle θD, the third angle θC and the fourth angle θD are within a following ranges:
• 6°≦θC≦26°
• 6°≦θD≦26°.

An acoustic wave element comprising:

• a piezoelectric substrate;
• an IDT electrode located on an upper surface of the piezoelectric substrate, wherein the IDT electrode comprises
• a first bus bar and a second bus bar which face each other in a direction which intersects with a propagation direction of the acoustic wave,
• a plurality of first electrode fingers which extend from the first bus bar to the second bus bar side,
• a plurality of second electrode fingers which extend from the second bus bar to the first bus bar side and have a portion adjacent to the plurality of first electrode fingers in the propagation direction,
• a plurality of first dummy electrodes which extend from the first bus bar to the second bus bar side and have tips which face the tips of the plurality of second electrode fingers through a plurality of first gaps, and
• a plurality of second dummy electrodes which extend from the second bus bar to the first bus bar side and have tips which face the tips of the plurality of first electrode fingers through a plurality of second gaps;
• a reflector which is adjacent to the IDT electrode in the propagation direction;
• and
• a protective layer which is located on the upper surface of the piezoelectric substrate so as to cover the IDT electrode and the reflector, and which has a larger thickness than those of the IDT electrode and the reflector,
• wherein, in a certain range of the propagation direction of the IDT electrode,
• when the arrangement direction of the first gaps among the plurality of first gaps which are adjacent to each other is the first direction, the first direction is inclined relative to the propagation direction,
• when the arrangement direction of the second gaps among the plurality of second gaps which are adjacent to each other is the second direction, the second direction is inclined to the side the same as the side to which the first direction is inclined relative to the propagation direction, and
• when the inclination angle of the first direction relative to the propagation direction is a first angle θA and the inclination angle of the second direction relative to the propagation direction is a second angle θB, the first angle θA and the second angle θB are within a following ranges:
• 10°≦θA≦26°
• 10°≦θB≦26°,
• wherein the reflector comprises
• a third bus bar on the first bus bar side and a fourth bus bar on the second bus bar side which face each other in the direction perpendicular to the propagation direction, and
• a plurality of third electrode fingers which extend so as to connect the third bus bar and the fourth bus bar, and
• wherein, when the reflectivity of the acoustic wave generating a primary resonance in the IDT electrode is Γ(%), the number of the third electrode fingers is within a following range:
• {100(%)/Γ(%)±1}.