A surface acoustic wave device includes a quartz layer, an amorphous silicon oxide layer, a piezoelectric layer, and an Inter Digital Transducer. The amorphous silicon oxide layer is laminated on the quartz layer. The piezoelectric layer is laminated on the amorphous silicon oxide layer. The Inter Digital Transducer is formed on the piezoelectric layer. The Inter Digital Transducer excites a surface acoustic wave on the piezoelectric layer. Assuming that the surface acoustic wave has a wavelength , 0.1a thickness of the amorphous silicon oxide layer/1, and 0.08a thickness of the piezoelectric layer/1.

A method of manufacturing a bonded substrate, which has a quartz substrate and a piezoelectric substrate bonded, includes irradiating a bonding surface of the quartz substrate and a bonding surface of the piezoelectric substrate with ultraviolet light under a pressure lower than atmosphere pressure. After the irradiation, the bonding surface of the quartz substrate and the bonding surface of the piezoelectric substrate are brought into contact. And the quartz substrate and the piezoelectric substrate are pressurized in a thickness direction to bond the bonding surfaces.

A surface acoustic wave device includes a quartz layer, a piezoelectric layer, and an Inter Digital Transducer. A rotation in a right-screw direction is assumed as a +-rotation. A three-dimensional coordinate system formed by an x1-axis, a y1-axis, and a z1-axis respectively matching an X-axis, a Y-axis, and a Z-axis as crystallographic axes of a quartz-crystal is rotated from +125.25 in a range of 3 with the x1-axis as a rotation axis. Subsequently, the three-dimensional coordinate system is rotated from +45 in a range of 2 with the z1-axis as the rotation axis. Subsequently, the three-dimensional coordinate system is rotated from 45 in a range of 2 with the x1-axis as the rotation axis. The quartz layer is cut along a surface as a sectional plane perpendicular to the z1-axis. The quartz layer has a propagation direction of the surface acoustic wave in a direction parallel to the x1-axis.

An acoustic wave sensor device comprises a first interdigitated transducer, a first reflection structure, a second reflection structure, a first resonance cavity comprising a first upper surface and formed between the first interdigitated transducer and the first reflection structure, and a second resonance cavity comprising a second upper surface and formed between the first interdigitated transducer and the second reflection structure. At least one of the first and second upper surfaces is covered at least partly by a metalization layer or a passivation layer. The present invention relates also to an acoustic wave sensor assembly.

An acoustic wave sensor device comprises a quartz material layer surface; arranged along a first axis, a first interdigitated transducer disposed over the planar surface of the quartz material layer, a first reflection structure disposed over the planar surface of the quartz material layer, and a second reflection structure disposed over the planar surface of the quartz material layer; and arranged along a second axis, a second interdigitated transducer disposed over the planar surface of the quartz material layer, a third reflection structure disposed over the planar surface of the quartz material layer, and a fourth reflection structure disposed over the planar surface of the quartz material layer; and wherein the first axis and the second axis are inclined to each other by a finite angle.

An acoustic wave element which can be reduced in size and produced relatively easily, practically used without using harmful substances, and can suppress a surface acoustic wave propagation loss, which has an excellent temperature coefficient of frequency and a velocity dispersion characteristic, and with which an increase in the reflection coefficient of interdigital transducers can be suppressed, and a method for manufacturing the acoustic wave element are provided. The acoustic wave element includes a pair of electrodes provided on both surfaces of a piezoelectric substrate, and a dielectric film provided on a first surface of the piezoelectric substrate so as to cover the electrode. The acoustic wave element alternatively includes interdigital transducers provided on a first surface of the piezoelectric substrate, and a dielectric film provided on the interdigital transducers, a gap between the interdigital transducers, and/or a second surface of the piezoelectric substrate.

There is provided a bonded substrate including: a quartz substrate; and a piezoelectric substrate which is bonded on the quartz substrate and on which a surface acoustic wave propagates, wherein the quartz substrate and the piezoelectric substrate are bonded at a bonding interface through covalent bonding, and a surface acoustic wave element having a higher phase velocity and a higher electromechanical coupling factor than conventional one is obtained by disposing an interdigital electrode on a principal surface of the piezoelectric substrate.

An elastic wave device includes a substrate, an IDT electrode, a spacer layer, a cover, and a protective layer. The spacer layer is provided on the substrate and surrounds the IDT electrode. The cover is provided on the spacer layer, is spaced apart from the IDT electrode, and includes a first main surface adjacent to the spacer layer and a second main surface facing the first main surface. The protective layer includes a third main surface contacting the second main surface, a fourth main surface facing the third main surface, and a side surface connected to the fourth main surface. In at least portion of the side surface of the protective layer, a portion including an intersection line between the side surface and the fourth main surface is located farther inward than an outer edge of the substrate in plan view in the thickness direction of the substrate.

An acoustic wave device includes a support substrate, a piezoelectric layer, and an IDT electrode. The support substrate is made of quartz. The piezoelectric layer is provided on the support substrate and is made of LiTaO.sub.3. The IDT electrode is on the piezoelectric layer and includes electrode fingers. The IDT electrode is on a negative surface side of the piezoelectric layer. The cut angle of the piezoelectric layer is equal to or more than about 39? Y and equal to or less than about 48? Y.

A surface acoustic wave device is disclosed. The surface acoustic wave device can include a single crystal support layer, an intermediate single crystal layer positioned over the single crystal support layer, a lithium based piezoelectric layer positioned over the intermediate single crystal layer, and an interdigital transducer electrode positioned over the lithium based piezoelectric layer, the surface acoustic wave device configured to generate a surface acoustic wave. The single crystal layer can be a quartz layer, such as a z-propagation quartz layer. A thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the intermediate single crystal layer, and the thermal conductivity of the single crystal support layer is greater than a thermal conductivity of the lithium based piezoelectric layer.