An acoustic wave device includes an interdigital transducer electrode connected to first and second terminals, and a reflector connected to the second terminal. In a group of electrode fingers of the interdigital transducer electrode, the electrode fingers at one end and another end in a second direction are respectively first and second end electrode fingers, the first end electrode finger includes a wide portion at a distal end portion. The first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An inner busbar portion of one of first and second busbars not connected to the first end electrode finger, is located on an inner side in the second direction relative to the wide portion of the first end electrode finger so as not to overlap the wide portion of the first end electrode finger in a first direction.

An acoustic wave device includes a piezoelectric substrate a reverse-velocity surface of which is convex, an interdigital transducer electrode disposed on the piezoelectric substrate, and mass addition films stacked above the interdigital transducer electrode. The interdigital transducer electrode includes a central region, first and second edge regions, first and second gap regions located outside the first and second edge regions, first and second inner busbar regions, and first and second outer busbar regions. The mass addition films are stacked in at least the first and second edge regions and the first and second inner busbar regions.

An elastic wave device includes an LiNbO.sub.3 substrate, a first elastic wave resonator including a first IDT electrode and a first dielectric film, and a second elastic wave resonator including a second IDT electrode and a second dielectric film. A Rayleigh wave travels along at least one surface of the elastic wave device. A thickness of the first dielectric film differs from a thickness of the second dielectric film. A propagation direction of an elastic wave in the first elastic wave resonator coincides with a propagation direction of an elastic wave in the second elastic wave resonator. Euler angles of the LiNbO.sub.3 substrate fall within a range of (0°±5°, θ, 0°±10°).

A high-frequency apparatus includes a first device and a second device, and a mounting substrate on which the first and second devices are mounted. At least the second device is an acoustic wave device including a piezoelectric substrate and a functional element. The first device and the second device are adjacent to or in a vicinity of each other on the mounting substrate. A coefficient of linear expansion of a substrate of the first device is lower than a coefficient of linear expansion of the mounting substrate, and a coefficient of linear expansion of the piezoelectric substrate of the second device is higher than the coefficient of linear expansion of the mounting substrate.

An acoustic wave device includes a support including a cavity, a piezoelectric layer on or above the support and made of one of lithium niobate or lithium tantalate, an interdigital transducer electrode embedded in the piezoelectric layer and including surfaces opposed to each other in a thickness direction, one of the surfaces being in contact with the piezoelectric layer, and a dielectric film on the piezoelectric layer and covering the interdigital transducer electrode. The interdigital transducer electrode includes electrode fingers, at least one of which overlaps the cavity in plan view. Assuming a thickness of the piezoelectric layer is d and an electrode finger pitch of the interdigital transducer electrode is p, p/d≥ about 4.25.

A transducer structure for a surface acoustic device comprises a composite substrate comprising a piezoelectric layer, a pair of inter-digitated comb electrodes, comprising a plurality of electrode means with a pitch p satisfying the Bragg condition, wherein the inter-digitated comb electrodes are embedded in the piezoelectric layer such that, in use, the excitation of a wave propagating mode in the volume of the electrode means is taking place and is the predominant propagating mode of the structure. The present disclosure relates also to an acoustic wave device comprising at least one transducer structure as described above and to a method for fabricating the transducer structure. The present disclosure relates also to the use of the frequency of the bulk wave propagating in the electrode means of the transducer structure in an acoustic wave device to generate contribution at high frequency, in particular, above 3 GHz.

A bonded body has a supporting substrate composed of silicon, a piezoelectric material substrate, and a bonding layer provided on a surface of the supporting substrate and composed of silicon oxide. The bonding layer has a refractive index of 1.468 or higher and 1.474 or lower.

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 μm to 0.4 μm, and there is satisfied either of the relationship between the arithmetic mean roughness (Ra) and mean spacing (S) of local peaks of Ra/S≥11, and the relationship between the arithmetic mean roughness (Ra) and mean spacing (Sm) of irregularities of Ra/Sm≥6.7. Further, the second surface has a maximum height (Rmax) of 2.5 μm to 4.5 μm, and there is satisfied either of the relationship between the maximum height (Rmax) and mean spacing (S) of local peaks of Rmax/S≥130, and the relationship between the maximum height (Rmax) and mean spacing (Sm) of irregularities of Rmax/Sm≥80.

An acoustic wave device includes a silicon oxide film, a piezoelectric body, and an interdigital transducer electrode laminated on a support substrate made of silicon. Where a wave length that is determined by an electrode finger pitch of the interdigital transducer electrode is λ, a thickness of the support substrate is greater than or equal to about 3λ. An acoustic velocity of the first higher mode that propagates through the piezoelectric body is an acoustic velocity V.sub.si=(V.sub.1).sup.1/2 of bulk waves that propagate in the support substrate, which is determined by V.sub.1 out of solutions V.sub.1, V.sub.2, and V.sub.3 of x derived from the mathematical expression Ax.sup.3+Bx.sup.2+Cx+D=0, or higher than V.sub.si.

An acoustic wave device, a radio frequency filter and an electronics module are provided. The acoustic wave device comprises a piezoelectric substrate, a temperature compensation layer disposed on the piezoelectric substrate, and an interdigital transducer embedded within the temperature compensation layer and spatially separated from the piezoelectric substrate. The interdigital transducer is configured to generate an acoustic wave in response to an electrical signal. A passivation layer is disposed on the temperature compensation layer. The acoustic wave device can be used in wide passband applications, and has an excellent temperature coefficient, small size, and a clean response.