In an elastic wave device, an IDT electrode is provided on a piezoelectric substrate and a first silicon oxide film covers the IDT electrode. A high-acoustic-velocity dielectric film covers the first silicon oxide film. A second silicon oxide film is provided on the high-acoustic-velocity dielectric film. The piezoelectric substrate is made of lithium niobate. The high-acoustic-velocity dielectric film propagates longitudinal waves at an acoustic velocity higher than an acoustic velocity of longitudinal waves propagating through the first silicon oxide film. The high-acoustic-velocity dielectric film is provided at a distance of about (t1+t2)×0.42 or less from a first main surface of the piezoelectric substrate in a thickness direction of the piezoelectric substrate.

A bonded body having a supporting substrate and piezoelectric material layer is provided. The supporting substrate is composed of mullite, and the material of the piezoelectric material layer is LiAO.sub.3 where A represents one or more element selected from the group consisting of niobium and tantalum. An interface layer is present along an interface between the supporting body and piezoelectric material layer, and a supporting substrate-side intermediate layer is present between the interface layer and supporting substrate. Each of the interface layer and supporting substrate-side intermediate layer contains oxygen, aluminum, silicon and one or more element selected from the group consisting of niobium and tantalum as main components.

An acoustic wave pressure sensor device configured to measure a pressure, comprising a substrate configured to bend when pressure is applied to the substrate such that an area of a first kind of strain and an area of a second kind of strain are formed in the substrate; an interdigitated transducer formed over the substrate; a first Bragg mirror formed over the substrate and arranged on one side of the interdigitated transducer; a second Bragg mirror formed over the substrate and arranged on another side of the interdigitated transducer; a first resonance cavity formed between the interdigitated transducer and the first Bragg mirror; a second resonance cavity formed between the interdigitated transducer and the second Bragg mirror; and wherein the first resonance cavity is formed over the area of the first kind of strain and the second resonance cavity is formed over the area of the second kind of strain.

An acoustic wave filter includes a substrate and a piezoelectric layer over the substrate. First acoustic wave resonators are disposed over the piezoelectric layer and arranged in series along a first branch, and second acoustic wave resonators are disposed over the piezoelectric layer, arranged in parallel, and connected to the first branch and to ground. The first and second acoustic wave resonators include an interdigital transducer electrode interposed between a pair of reflectors. A layer of negative temperature coefficient of frequency dielectric material is disposed over one or more of the second plurality of acoustic wave resonators to control the temperature coefficient of frequency and improve temperature stability of the acoustic wave filter.

In a bonded substrate according to an embodiment, Euler angles (φ1, θ1, ψ1) of a first quartz-crystal substrate satisfy 0°≤φ1≤2°, 123°≤θ1≤128°, and 31°≤ψ1≤44°, Euler angles (φ2, θ2, ψ2) of a second quartz-crystal substrate bonded over the first quartz-crystal substrate satisfy 83°≤φ2≤95°, 82°≤θ2≤95°, and 159°≤ψ2≤161°, and a thickness of the second quartz-crystal substrate is 0.17 to 0.19 times a wavelength of a surface acoustic wave.

An acoustic wave device includes a piezoelectric material substrate, an intermediate layer on the piezoelectric material substrate and composed of one or more materials selected from the group consisting of silicon oxide, aluminum nitride and sialon. A bonding layer is on the intermediate layer and is composed of one or more materials selected from the group consisting of tantalum pentoxide, niobium pentoxide, titanium oxide, mullite, alumina, and a high resistance silicon and hafnium oxide. A supporting body is composed of a polycrystalline ceramic and is bonded to the bonding layer by direct bonding, and an electrode is on the piezoelectric material substrate.

A circuit device formed from a functional substrate. The circuit device comprises a functional substrate component and printed electronic elements formed on the functional substrate component. The printed electronic elements formed on the functional substrate component interact with the substrate component to perform a function and to modify the functional substrate component. The circuit device typically needs a passive base material that takes no functional part in the device operation except mechanical support.

Surface acoustic wave resonators are disclosed. In certain embodiments, a surface acoustic wave resonator can include a high impedance layer, a piezoelectric layer over the high impedance layer, an interdigital transducer electrode over the piezoelectric layer, and a low impedance layer between the high impedance layer and the piezoelectric layer. An acoustic impedance of the high impedance layer is greater than an acoustic impedance of the piezoelectric layer. An acoustic impedance of the low impedance layer is lower than the acoustic impedance of the high impedance layer. The piezoelectric layer can have a cut angle in a range from 115° to 135°. The surface acoustic wave resonator is configured to generate a Rayleigh mode surface acoustic wave having a wavelength of λ.

A composite substrate capable of improving temperature characteristics while suppressing crack generation and a method for manufacturing such composite substrate is provided. The method for manufacturing composite substrates includes: a step of preparing a piezoelectric material substrate having a rough surface; a step of removing the damaged layer by etching the rough surface of the piezoelectric material substrate using a chemical process; a step of depositing an intervening layer on the rough surface of the piezoelectric material substrate from which the damaged layer has been removed; a step of flattening the surface of the deposited intervening layer; a step of bonding the piezoelectric material substrate to a support substrate having a lower thermal expansion coefficient than the piezoelectric material, with the deposited intervening layer in between; and a step of thinning the piezoelectric material substrate after bonding. Lithium tantalate (LT) or lithium niobate (LN) are suitable as the piezoelectric material.

An acoustic wave device includes a piezoelectric layer made of lithium niobate or lithium tantalate and including a first main surface, and an IDT electrode and a first dielectric film on the first main surface. A ratio d/p is equal to or less than about 0.5, when a thickness of the piezoelectric layer is d and a center-to-center distance between adjacent electrodes is p. The first dielectric film includes first and second surfaces facing each other. The second surface is a surface on a side of the piezoelectric layer. The IDT electrode includes third and fourth surfaces facing each other. The fourth surfaces are on the side of the piezoelectric layer. The first surface of the first dielectric film is at a same height as or higher than the third surfaces of the IDT electrode. A second dielectric film is on the first surface of the first dielectric film.