An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity V.sub.si=(V.sub.1).sup.1/2 of propagation through silicon or higher than the acoustic velocity V.sub.si, where V.sub.si is specified by V.sub.1 among solutions V.sub.1, V.sub.2, and V.sub.3 with respect to x derived from Ax.sup.3+Bx.sup.2+Cx+D=0.

A radio-frequency module includes a module substrate, an inductor, and an acoustic wave filter. The inductor overlaps at least a portion of the acoustic wave filter when seen in a plan view from the normal direction of the module substrate. The inductor includes first and second coils connected in series. Each of the first and second coils is a spiral or helical coil that is wound with more than one turn. At least a portion of the first coil overlaps the second coil when seen in a plan view from the normal direction of the module substrate. A direction of a magnetic field generated by the first coil is opposite to a direction of a magnetic field generated by the second coil.

A composite substrate includes: a piezoelectric layer; and a reflective layer arranged on a rear surface side of the piezoelectric layer, wherein the reflective layer includes a high-impedance layer and a low-impedance layer containing silicon oxide, and wherein a ratio of a region of first structures in the high-impedance layer is more than 70%.

A piezoelectric device includes a support substrate, an intermediate layer on the support substrate, a piezoelectric layer on the intermediate layer, a functional element on the piezoelectric layer, an insulation layer, and a wiring electrode. The insulation layer is on the support substrate and in contact with the intermediate layer and the piezoelectric layer. The wiring electrode extends from a top of the insulation layer to a top of the piezoelectric layer and is connected to the functional element. The insulation layer includes first and second regions. The first region is thinner than a thickness of the multilayer body. The second region connects the first region and the multilayer body, and includes a portion slanted from the first region toward an upper surface of the piezoelectric layer. The second region of the insulation layer does not extend to the top of the piezoelectric layer.

The invention relates to a method for manufacturing an electroacoustic resonator comprising the steps of: Providing a first substrate having a first side and an opposite second side; depositing a diamond layer having a first side and an opposite second side on said first substrate, wherein the second side of the diamond layer is in contact with said first side of the first substrate; removing the first substrate; forming a piezoelectric layer on the second side of the diamond layer; applying a second substrate to the first side of the diamond layer.

An acoustic wave device can have a plurality of coupling portions configured to electrically couple electrodes of the device to the substrate of the device to provide a bypass current pathway through the substrate for heat management. The substrate can be a semiconductor material, which can become more conductive as the temperature increases so that the bypass current pathway diverts more power through the substrate as the temperature increases. The acoustic wave device can be a surface acoustic wave device, which can have an interdigital transducer electrode that has the coupling portions on each of the bus bars and extending through the piezoelectric layer to contact the substrate. The acoustic wave device can be a bulk acoustic wave device in some implementations.

A surface acoustic wave resonator comprises a multi-layer piezoelectric substrate including a carrier substrate, a layer of a first dielectric material disposed on a front side of the carrier substrate, and a layer of piezoelectric material disposed on a front side of the layer of the first dielectric material, the piezoelectric material having a cut angle θ of from about 12 degrees to about 25 degrees to suppress bulk leakage and improve gamma, and interdigital transducer electrodes disposed on a front side of the layer of piezoelectric material.

An acoustic wave device includes a piezoelectric layer, first and second upper electrodes, first and second lower electrodes, and first and second acoustic reflection films. In plan view, first and second resonator portions are respectively defined by portions where the first upper electrode and the first lower electrode overlap and where the second upper electrode and the second lower electrode overlap. The first and second acoustic reflection films respectively include first and second metal layers. First and second overlapping portions are respectively defined by portions where only the first upper electrode overlaps with the first metal layer and where only the second upper electrode overlaps with the second metal layer. An area of the first resonator portion is smaller than an area of the second resonator portion and an area of the first overlapping portion is larger than an area of the second overlapping portion.

A filter device includes a first series line, one or more first parallel lines extending from the first series line, two or more first series IDT electrodes on the first series line, and one or more first parallel IDT electrodes on the one or more first parallel lines. At least one of the two or more first series IDT electrodes is a first-type electrode. A dielectric layer is between the first-type electrode and a substrate. At least one of the two or more first series IDT electrodes except the first-type electrode and the one or more first parallel IDT electrodes is a second-type electrode directly contacting the substrate. A first series IDT electrode of the two or more first series IDT electrodes that has a largest pitch of electrode fingers is the first-type electrode.

A surface acoustic wave resonator comprises a multi-layer piezoelectric substrate including a carrier substrate, a layer of a first dielectric material disposed on the carrier substrate, and a layer of piezoelectric material disposed on the layer of the first dielectric material, interdigital transducer electrodes disposed on the layer of piezoelectric material and including interleaved electrode fingers, and a layer of a second dielectric material disposed on a central interleaved region of the interleaved electrode fingers, gap regions of the interdigital transducer electrodes being either free of the layer of the second dielectric material or having a thinner layer of the second dielectric material than the central interleaved region to reduce spurious signals in an admittance curve of the surface acoustic wave resonator.