Acoustic wave device and filter device

An acoustic wave device, comprising:

• a piezoelectric substrate including a piezoelectric layer;
• and
• an IDT electrode on the piezoelectric layer;
• wherein
• the IDT electrode includes:
• a first busbar and a second busbar facing each other;
• a plurality of first electrode fingers each of which includes one end connected to the first busbar;
• and
• a plurality of second electrode fingers each of which includes one end connected to the second busbar;
• the plurality of first electrode fingers and the plurality of second electrode fingers are interdigitated with each other;
• a portion where the plurality of first electrode fingers and the plurality of second electrode fingers overlap in an acoustic wave propagation direction is an intersecting region;
• a shape of the pluralities of first and second electrode fingers in plan view includes a shape of a circular arc or an elliptical arc;
• and
• an electrode finger pitch decreases as an absolute value of an angle θc increases, where the angle θc is an angle between a straight line passing through a fixed point and a reference line, the fixed point being a center of a circle including the circular arc of the shape of the first and second electrode fingers or a midpoint between two foci of an ellipse including the elliptical arc, the reference line being a straight line passing through a center of the intersecting region in a direction in which the pluralities of first and second electrode fingers extend.

An acoustic wave device, comprising:

• a piezoelectric substrate including a piezoelectric layer;
• and
• an IDT electrode on the piezoelectric layer;
• wherein
• the piezoelectric substrate is one of a substrate including a stack of a support substrate and the piezoelectric layer including lithium tantalate or lithium niobate or a substrate including only the piezoelectric layer including lithium niobate;
• the IDT electrode includes:
• a first busbar and a second busbar facing each other;
• a plurality of first electrode fingers each of which includes one end connected to the first busbar;
• and
• a plurality of second electrode fingers each of which includes one end connected to the second busbar;
• the plurality of first electrode fingers and the plurality of second electrode fingers are interdigitated with each other;
• a portion where the plurality of first electrode fingers and the plurality of second electrode fingers overlap in an acoustic wave propagation direction is an intersecting region;
• a shape of the pluralities of first and second electrode fingers in plan view includes a shape of a circular arc or an elliptical arc;
• and
• the pluralities of first and second electrode fingers have one of a configuration in which electrode finger pitch increases as an absolute value of an angle θc increases or a configuration in which the electrode finger pitch decrease as the absolute value of the angle θc increases where the angle θc is an angle between a straight line passing through a fixed point and a reference line, the fixed point being a center of a circle including the circular arc of the shape of the first and second electrode fingers or a midpoint between two foci of an ellipse including the elliptical arc, the reference line being a straight line passing through a center of the intersecting region in a direction in which the pluralities of first and second electrode fingers extend.