Acoustic wave device

An acoustic wave device comprising:

• a support substrate including a recess;
• a piezoelectric film covering the recess of the support substrate and defining a cavity together with the recess;
• and
• a functional electrode on the piezoelectric film;
• wherein
• the functional electrode includes:
• first and second busbars;
• at least one first electrode finger including one end connected to the first busbar;
• and
• at least one second electrode finger including one end connected to the second busbar;
• and
• when an overlap region is defined as a region in which the first and second electrode fingers overlap each other in an acoustic wave propagation direction, points A2, B2, C2, and D2 are all inside the cavity when, at the points A2, B2, C2, and D2,
• xa<about 2 μm, ya<about 2 μm;
• xb<about 2 μm, yb<about 2 μm;
• xc<about 2 μm, yc<about 2 μm;
• xd<about 2 μm, and yd<2 about μm;
• the points A2, B2, C2, and D2 being defined as follows:
• point A2:
• a point shifted from a point A1 as a starting point by xa in an x direction and by ya in a y direction toward the outside of the overlap region;
• point B2:
• a point shifted from a point B1 as a starting point by xb in the x direction and by yb in the y direction toward the outside of the overlap region;
• point C2:
• a point shifted from a point C1 as a starting point by xc in the x direction and by yc in the y direction toward the outside of the overlap region;
• and
• point D2:
• a point shifted from a point D1 as a starting point by xd in the x direction and by yd in the y direction toward the outside of the overlap region;
• and
• the points A1, B1, C1, and D1 being defined as follows:
• point A1:
• an intersection of an outer edge of an outermost electrode on one end side in the acoustic wave propagation direction and the first busbar;
• point B1:
• an intersection of an extension line of an outer edge of an outermost electrode on another end side in the acoustic wave propagation direction and the first busbar;
• point C1:
• an intersection of an extension line of the outer edge of the outermost electrode on the one end side in the acoustic wave propagation direction and the second busbar;
• and
• point D1:
• an intersection of the outer edge of the outermost electrode on the other end side in the acoustic wave propagation direction and the second busbar.

An acoustic wave device comprising:

• a support substrate including a cavity;
• a piezoelectric film on the support substrate;
• and
• a functional electrode on the piezoelectric film;
• wherein
• the functional electrode includes:
• first and second busbars;
• at least one first electrode finger including one end connected to the first busbar;
• and
• at least one second electrode finger including one end connected to the second busbar;
• and
• when an overlap region is defined as a region in which the first and second electrode fingers overlap each other in an acoustic wave propagation direction, points A2, B2, C2, and D2 are all outside the cavity when, at the points A2, B2, C2, and D2,
• xa>about 25 μm, ya>about 25 μm;
• xb>about 25 μm, yb>about 25 μm;
• xc>about 25 μm, yc>about 25 μm;
• xd>about 25 μm, and yd>about 25 μm;
• and
• the points A2, B2, C2, and D2 are all inside the cavity when, at the points A2, B2, C2, and D2,
• xa<about 2 μm, ya<about 2 μm;
• xb<about 2 μm, yb<about 2 μm;
• xc<about 2 μm, yc<about 2 μm;
• xd<about 2 μm, and yd<about 2 μjm;
• the points A2, B2, C2, and D2 being defined as follows:
• point A2:
• a point shifted from a point A1 as a starting point by xa in an x direction and by ya in a y direction toward the outside of the overlap region;
• point B2:
• a point shifted from a point B1 as a starting point by xb in the x direction and by yb in the y direction toward the outside of the overlap region;
• point C2:
• a point shifted from a point C1 as a starting point by xc in the x direction and by yc in the y direction toward the outside of the overlap region;
• and
• point D2:
• a point shifted from a point D1 as a starting point by xd in the x direction and by yd in the y direction toward the outside of the overlap region;
• the points A1, B1, C1, and D1 being defined as follows:
• point A1:
• an intersection of an outer edge of an outermost electrode on one end side in the acoustic wave propagation direction and the first busbar;
• point B1:
• an intersection of an extension line of an outer edge of an outermost electrode on another end side in the acoustic wave propagation direction and the first busbar;
• point C1:
• an intersection of an extension line of the outer edge of the outermost electrode on the one end side in the acoustic wave propagation direction and the second busbar;
• and
• point D1:
• an intersection of the outer edge of the outermost electrode on the other end side in the acoustic wave propagation direction and the second busbar.