Aspects of this disclosure relate to a surface acoustic wave device that includes a first reflector over a piezoelectric layer, a second reflector over the piezoelectric layer, and an interdigital transducer electrode structure over the piezoelectric layer and positioned between the first reflector and the second reflector. The surface acoustic wave device includes a velocity adjustment layer arranged to adjust acoustic velocity in a region of the surface acoustic wave device. The velocity adjustment layer can be a high speed layer or a low speed layer.

A sensor device that includes an integrated sensor assembly having a surface acoustic wave (SAW) sensor disposed on a piezoelectric substrate. The SAW sensor is adapted to measure an environmental condition of an environment in response to an RF signal. The SAW sensor includes an interdigitated transducer (IDT) formed on a substrate having at least a layer of a piezoelectric material. The SAW sensor includes either one or more SAW reflectors of a second IDT formed on the piezoelectric material. The SAW sensor further includes an RF antenna formed on the piezoelectric material. The SAW sensor and the RF antenna are integrated with one another on the piezoelectric material.

A substrate for a surface acoustic wave device is constituted of a piezoelectric material and includes a first surface on which a surface acoustic wave propagates, and a second surface located opposite to the first surface. The second surface has an arithmetic mean roughness (Ra) of 0.2 m to 0.4 m, and there is satisfied either of the relationship between the arithmetic mean roughness (Ra) and mean spacing (S) of local peaks of Ra/S11, and the relationship between the arithmetic mean roughness (Ra) and mean spacing (Sm) of irregularities of Ra/Sm6.7. Further, the second surface has a maximum height (Rmax) of 2.5 m to 4.5 m, and there is satisfied either of the relationship between the maximum height (Rmax) and mean spacing (S) of local peaks of Rmax/S130, and the relationship between the maximum height (Rmax) and mean spacing (Sm) of irregularities of Rmax/Sm80.

An acoustic wave device includes a piezoelectric substrate, an interdigital transducer electrode on the piezoelectric substrate, and two reflectors on both sides of the interdigital transducer electrode in an acoustic wave propagation direction. The reflectors include first and second busbars and first to third electrode fingers, respectively, and the first and second busbars are opposed to one another. The first busbars and the second busbars are connected by at least one third electrode finger. The reflectors each include a center area located centrally in a length direction and a first high-acoustic-velocity area that is located between the center area and the first busbars and has an acoustic velocity higher than the acoustic velocity of the center area, where the length direction is a direction in which the first to third electrode fingers extend.

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.

Aspects of this disclosure relate to a surface acoustic wave filter with an acoustic velocity adjustment structure. The surface acoustic wave filter can include a first interdigital transducer electrode disposed on a piezoelectric layer, an acoustic reflector disposed on the piezoelectric layer, and a second interdigital transducer electrode disposed on the piezoelectric layer. The second interdigital transducer electrode is longitudinally coupled to the first interdigital transducer electrode and positioned between the first interdigital transducer electrode and the acoustic reflector. The acoustic velocity adjustment structure can be positioned over at least a gap between the first interdigital transducer electrode and the second interdigital transducer electrode. The acoustic velocity adjustment structure can be arranged to increase an acoustic wave propagation velocity in a first region that includes the gap relative to a second region over at least a portion of the first interdigital transducer electrode.

[Object] An object of the present invention is to provide a bonded substrate which is excellent in temperature characteristics and suppresses unnecessary response due to reflection of an elastic wave at a bonding interface.

[Means to Solve the Problems] The present invention is unique in that a bonded substrate is constructed by bonding a LiTaO.sub.3 substrate and a base plate wherein a Li concentration at a base plate-bonding face of the LiTaO.sub.3 substrate is higher than that at a LiTaO.sub.3 substrate-side end face of the bonded substrate, that the difference between the Li concentration at the base plate-bonding face of the LiTaO.sub.3 substrate and the Li concentration at the LiTaO.sub.3 substrate-side end face of the bonded substrate is 0.1 mol % or greater, that the Li concentration at the base plate-bonding face of the LiTaO.sub.3 substrate satisfies an equation Li/(Li+Ta)100=(50+) mol %, where is in the range of 1.2<<0.5, that the Li concentration at the LiTaO.sub.3 substrate-side end face of the bonded substrate satisfies an equation Li/(Li+Ta)100=(48.5+) mol %, where is in the range of 0.5<<0.5, and that the thickness measured from the base plate-bonding face of the LiTaO.sub.3 substrate to the LiTaO.sub.3 substrate-side end face of the finished bonded substrate becomes greater than 5 times but less than 20 times the wavelength of the surface acoustic wave or that of the leaky surface acoustic wave.

A sensor device that includes an integrated sensor assembly having a surface acoustic wave (SAW) sensor disposed on a piezoelectric substrate. The SAW sensor is adapted to measure an environmental condition of an environment in response to an RF signal. The SAW sensor includes an interdigitated transducer (IDT) formed on a substrate having at least a layer of a piezoelectric material. The SAW sensor includes either one or more SAW reflectors of a second IDT formed on the piezoelectric material. The SAW sensor further includes an RF antenna formed on the piezoelectric material. The SAW sensor and the RF antenna are integrated with one another on the piezoelectric material.

An electro-acoustic component with improved acoustics is specified. The component comprises a rectangular chip whose side edges are rotated relative to the piezoelectric axis.

A method of manufacturing surface acoustic wave device chips includes grinding a reverse side of a wafer with a surface acoustic wave device formed in each area demarcated by a plurality of crossing projected dicing lines on a face side of the wafer; before or after grinding, applying a laser beam to the reverse side of the wafer such that the laser beam is focused at a position within the wafer, the position being closer to the face side of the wafer than a position corresponding to a reverse side of each of the surface acoustic wave device chips to be produced from the wafer, thereby forming a modified layer for diffusing an acoustic wave; and after grinding and applying the laser beam, dividing the wafer along the projected dicing lines into a plurality of the surface acoustic wave device chips.