An elastic wave device includes a supporting substrate, an acoustic reflection layer disposed on the supporting substrate, a piezoelectric layer disposed on the acoustic reflection layer, and an interdigital transducer electrode disposed on the piezoelectric layer. The acoustic reflection layer includes three or more low acoustic impedance layers and two or more high acoustic impedance layers. A film thickness of the low acoustic impedance layer closest to the piezoelectric layer is larger than a film thickness of the low acoustic impedance layer closest to the low acoustic impedance layer that is closest to the piezoelectric layer.

A through-hole that extends from an upper surface of a cover opposite a support to a lower surface of the support facing a substrate is provided in the support and the cover. The through-hole overlaps a portion of a wiring line in a plan view. An acoustic wave device further includes an electrode film that is electrically connected to the wiring line in the through-hole, and a protective layer that includes an insulating material and that covers a portion of the electrode film. The protective layer is connected to the cover and the support in the through-hole. Differences in thermal expansion coefficients between the protective layer and the cover and between the protective layer and the support are smaller than a difference in thermal expansion coefficients between the protective layer and the electrode film.

A through-hole that extends from an upper surface of a cover opposite a support to a lower surface of the support facing a substrate is provided in the support and the cover. The through-hole overlaps a portion of a wiring line in a plan view. An acoustic wave device further includes an electrode film that is electrically connected to the wiring line in the through-hole, and a protective layer that includes an insulating material and that covers a portion of the electrode film. The protective layer is connected to the cover and the support in the through-hole. Differences in thermal expansion coefficients between the protective layer and the cover and between the protective layer and the support are smaller than a difference in thermal expansion coefficients between the protective layer and the electrode film.

The present invention relates to a heterostructure, in particular, a piezoelectric structure, comprising a cover layer, in particular, a layer of piezoelectric material, the material of the cover layer having a first coefficient of thermal expansion, assembled to a support substrate, the support substrate having a second coefficient of thermal expansion substantially different from the first coefficient of thermal expansion, at an interface wherein the cover layer comprises at least a recess extending from the interface into the cover layer, and its method of fabrication.

The present invention relates to a heterostructure, in particular, a piezoelectric structure, comprising a cover layer, in particular, a layer of piezoelectric material, the material of the cover layer having a first coefficient of thermal expansion, assembled to a support substrate, the support substrate having a second coefficient of thermal expansion substantially different from the first coefficient of thermal expansion, at an interface wherein the cover layer comprises at least a recess extending from the interface into the cover layer, and its method of fabrication.

An acoustic wave device includes: a piezoelectric substrate; a comb-shaped electrode located on the piezoelectric substrate; a wiring layer located on the piezoelectric substrate and electrically connected with the comb-shaped electrode; a first insulating film located on the piezoelectric substrate, the first insulating film covering the comb-shaped electrode, having an aperture on the wiring layer, and being thicker than the comb-shaped electrode; a second insulating film covering an upper surface of the first insulating film and at least a part of a side surface of the first insulating film in the aperture and having a higher moisture resistance than the first insulating film; and a pad being in contact with the wiring layer exposed by the aperture.

An acoustic wave device includes: a piezoelectric substrate; a comb-shaped electrode located on the piezoelectric substrate; a wiring layer located on the piezoelectric substrate and electrically connected with the comb-shaped electrode; a first insulating film located on the piezoelectric substrate, the first insulating film covering the comb-shaped electrode, having an aperture on the wiring layer, and being thicker than the comb-shaped electrode; a second insulating film covering an upper surface of the first insulating film and at least a part of a side surface of the first insulating film in the aperture and having a higher moisture resistance than the first insulating film; and a pad being in contact with the wiring layer exposed by the aperture.

A method of manufacturing an acoustic wave device is disclosed. The method includes attaching a support layer to a ceramic layer. The support layer has a higher thermal conductivity than the ceramic layer. The ceramic layer can be a polycrystalline spinel layer. The method also includes bonding a piezoelectric layer to a surface of the ceramic layer. The method further includes forming an interdigital transducer electrode over the piezoelectric layer.

A method of manufacturing an acoustic wave device is disclosed. The method includes attaching a support layer to a ceramic layer. The support layer has a higher thermal conductivity than the ceramic layer. The ceramic layer can be a polycrystalline spinel layer. The method also includes bonding a piezoelectric layer to a surface of the ceramic layer. The method further includes forming an interdigital transducer electrode over the piezoelectric layer.

An acoustic wave device is disclosed. The acoustic wave device includes a support layer, a ceramic layer positioned over the support layer, a piezoelectric layer positioned over the ceramic layer, and an interdigital transducer electrode positioned over the piezoelectric layer. The support layer has a higher thermal conductivity than the ceramic layer. The ceramic layer can be a polycrystalline spinel layer. The acoustic wave device can be a surface acoustic wave device configured to generate a surface acoustic wave.