Abstract: An acoustic wave device includes a support substrate having a thickness in a first direction, a piezoelectric layer on the support substrate, an interdigital transducer electrode on the piezoelectric layer and including first and second electrode fingers, the first electrode fingers extending in a second direction crossing the first direction, the second electrode fingers extending in the second direction and facing the first electrode fingers in a third direction orthogonal or substantially orthogonal to the second direction, and a reinforcing film on the piezoelectric layer. The support substrate and the piezoelectric layer include a hollow therebetween at a position overlapping the interdigital transducer electrode in the first direction. At least one through hole penetrates the piezoelectric layer at a position not overlapping the interdigital transducer electrode in the first direction, and the through hole communicates with the hollow. The reinforcing film overlaps the hollow in the first direction.

Abstract: An acoustic wave device includes a support substrate, an inorganic film over the support substrate, a piezoelectric layer over the inorganic film, and an electrode over the piezoelectric layer. A portion of the support substrate includes a hollow that overlaps at least a portion of the electrode in a thickness direction of the support substrate. An inner wall of the inorganic film is located farther from the hollow than a location on an inner wall of the support substrate, the location being closest to the piezoelectric layer, the inner wall of the support substrate defining the hollow.

Abstract: An acoustic wave device includes a support substrate, a piezoelectric layer overlapping the support substrate viewed in a first direction, a functional electrode on at least a first main surface of the piezoelectric layer, and a wiring electrode connected to the functional electrode. A space is provided on a second main surface side opposite to the first main surface of the piezoelectric layer. The space is covered with the piezoelectric layer, the wiring electrode covers a portion of the functional electrode, and an air gap or an insulating film is provided between the functional electrode and the wiring electrode in a region where the functional electrode is covered with the wiring electrode.

Abstract: An acoustic wave device includes a piezoelectric film and an IDT electrode on the piezoelectric film. The IDT electrode includes first and second busbars, at least one first electrode finger, and at least one second electrode finger. 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, defined as follows, are all outside the cavity when, at the points A2, B2, C2, and D2, xa>about 25 ?m, ya>about 25 ?m, xb>about 25 ?m, yb>about 25 ?m, xc>about 25 ?m, yc>about 25 ?m, xd>about 25 ?m, and yd>about 25 ?m.

Abstract: An elastic wave device includes a piezoelectric film made of lithium niobate or lithium tantalate, and a first electrode finger and a second electrode finger opposing each other in a direction intersecting a thickness direction of the piezoelectric film. When an average thickness of the piezoelectric film is d and a distance between centers of the first electrode finger and the second electrode finger is p, d/p is about 0.5 or less. The first electrode finger and the second electrode finger are connected to the first and second bus bars, respectively. The first and second bus bars include corner portions. At least one of corner portions of the first and second bus bars is outside a cavity portion when viewed in plan view.

Abstract: A manufacturing method for a boundary acoustic wave device is provided which includes, an IDT electrode, a first dielectric layer, and a second dielectric layer on a piezoelectric substrate. The first dielectric layer is made of a deposited film. A thickness of the IDT electrode is about 10% or more of ?. A difference between a height of the first dielectric layer, measured from an upper surface of the piezoelectric substrate, above a center of an electrode finger of the IDT electrode and a height of the first dielectric layer, measured from the upper surface of the piezoelectric substrate, above a center of a gap between adjacent electrode fingers, i.e., a magnitude of unevenness in an upper surface of the first dielectric layer, is about 5% or less of ?.

Abstract: In the boundary acoustic wave device, an IDT electrode, a first dielectric layer, and a second dielectric layer are provided on a piezoelectric substrate. The first dielectric layer is made of a deposited film. A thickness of the IDT electrode is about 10% or more of ?. A difference between a height of the first dielectric layer, measured from an upper surface of the piezoelectric substrate, above a center of an electrode finger of the IDT electrode and a height of the first dielectric layer, measured from the upper surface of the piezoelectric substrate, above a center of a gap between adjacent electrode fingers, i.e., a magnitude of unevenness in an upper surface of the first dielectric layer, is about 5% or less of ?.

Abstract: In the boundary acoustic wave device, an IDT electrode, a first dielectric layer, and a second dielectric layer are provided on a piezoelectric substrate. The first dielectric layer is made of a deposited film. A thickness of the IDT electrode is about 10% or more of ?. A difference between a height of the first dielectric layer, measured from an upper surface of the piezoelectric substrate, above a center of an electrode finger of the IDT electrode and a height of the first dielectric layer, measured from the upper surface of the piezoelectric substrate, above a center of a gap between adjacent electrode fingers, i.e., a magnitude of unevenness in an upper surface of the first dielectric layer, is about 5% or less of ?.

Abstract: In the boundary acoustic wave device, an IDT electrode, a first dielectric layer, and a second dielectric layer are provided on a piezoelectric substrate. The first dielectric layer is made of a deposited film. A thickness of the IDT electrode is about 10% or more of ?. A difference between a height of the first dielectric layer, measured from an upper surface of the piezoelectric substrate, above a center of an electrode finger of the IDT electrode and a height of the first dielectric layer, measured from the upper surface of the piezoelectric substrate, above a center of a gap between adjacent electrode fingers, i.e., a magnitude of unevenness in an upper surface of the first dielectric layer, is about 5% or less of ?.

Abstract: A method for manufacturing a boundary acoustic wave device prevents formation of discontinuous portions in a dielectric film without a significant decrease in the thickness of an IDT when the dielectric film is formed by deposition and without deterioration of electrical characteristics. The method includes the steps of forming an IDT on a piezoelectric substrate, forming a lower dielectric film so as to cover the IDT, conducting a planarizing step so as to smooth the rough surface of the lower dielectric film, and forming an upper dielectric film so as to cover the lower dielectric film of which the rough surface is smoothed.

Abstract: A method for manufacturing a boundary acoustic wave device prevents formation of discontinuous portions in a dielectric film without a significant decrease in the thickness of an IDT when the dielectric film is formed by deposition and without deterioration of electrical characteristics. The method includes the steps of forming an IDT on a piezoelectric substrate, forming a lower dielectric film so as to cover the IDT, conducting a planarizing step so as to smooth the rough surface of the lower dielectric film, and forming an upper dielectric film so as to cover the lower dielectric film of which the rough surface is smoothed.