An acoustic wave device includes a support substrate, a multilayer body, and an IDT electrode. The multilayer body includes a lithium tantalate piezoelectric layer and a lithium niobate piezoelectric layer that are laminated, and is on the support substrate. The IDT electrode is on the multilayer body, and includes electrode fingers. When a wavelength of an acoustic wave determined by a pitch of the electrode fingers is denoted as λ, a thickness of the multilayer body is about 0.66λ or less.

A acoustic wave resonator comprises a piezoelectric substrate and a plurality of interdigital transducer (IDT) electrodes disposed on the piezoelectric substrate, the plurality of IDT electrodes formed of a mixture of tungsten and chromium to provide for reduction in size and increase in quality factor of the acoustic wave resonator.

An elastic wave device includes a piezoelectric film, a high acoustic velocity member, a low acoustic velocity film located between the piezoelectric film and the high acoustic velocity member and through which an elastic wave propagates at a lower acoustic velocity than an elastic wave that propagates through the piezoelectric film, and an interdigital transducer electrode including electrode fingers separated from each other and disposed side by side in a first direction. At least one of the electrode fingers includes a first metal layer including first and second main body portions. A recessed portion is located in a central region in the first direction of the electrode finger and is recessed in the thickness direction of the piezoelectric film. A protrusion portion protrudes from at least a portion of the first main body portion in the first direction.

A surface acoustic wave device (5) is provided using a layered substrate system with a special material and a special cut of a piezoelectric thin film (4) selected for utilizing Rayleigh mode. The proper choice of the material and the cut of the piezoelectric thin film leads to a low velocity of the excited wave mode, which allows the usage of smaller devices without deteriorating other performance parameters according to specifications.

An acoustic wave device includes a piezoelectric substrate, a pair of interleaved interdigital transducer electrodes disposed on the piezoelectric substrate, and a dielectric film including silicon oxynitride covering the pair of interleaved interdigital transducer electrodes. The dielectric film exhibits a temperature coefficient of velocity of substantially zero throughout an operating temperature range of the acoustic wave device of between −55° C. and 125° C.

An elastic wave device includes a supporting substrate, a high-acoustic-velocity film stacked on the supporting substrate and in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an elastic wave propagating in a piezoelectric film, a low-acoustic-velocity film stacked on the high-acoustic-velocity film and in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric film, the piezoelectric film is stacked on the low-acoustic-velocity film, and an IDT electrode stacked on a surface of the piezoelectric film.

An elastic wave device includes a piezoelectric substrate, an IDT electrode on the piezoelectric substrate, and a silicon oxide film arranged on the piezoelectric substrate to cover the IDT electrode. The IDT electrode includes first and second electrode layers laminated on each other, the first electrode layer is made of metal or an alloy with a density higher than a density of metal of the second electrode layer and a density of silicon oxide of the silicon oxide film, the piezoelectric substrate is made of LiNbO.sub.3 and θ is in a range of equal to or greater than about 8° and equal to or less than about 32° with Euler Angles (0°±5°, θ, 0°±10°) of the piezoelectric substrate, and the silicon oxide film contains hydrogen atoms, hydroxyl groups, or silanol groups.

An acoustic wave resonator includes: a support substrate; a piezoelectric substrate located on the support substrate; a first amorphous layer that is in contact with the support substrate and is mainly composed of one or more constituent elements of the support substrate; a second amorphous layer that is in contact with the piezoelectric substrate and the first amorphous layer, is mainly composed of one or more constituent elements of the piezoelectric substrate, and is thinner than the first amorphous layer; and a pair of comb-shaped electrodes that is located on an opposite surface of the piezoelectric substrate from the support substrate, each of the pair of comb-shaped electrodes including electrode fingers.

An acoustic wave device includes a piezoelectric layer, an IDT electrode, a high-acoustic-velocity support substrate, and a low-acoustic-velocity film. The high-acoustic-velocity support substrate is located on an opposite side of the piezoelectric layer from the IDT electrode in the thickness direction of the piezoelectric layer. The low-acoustic-velocity film is disposed between the high-acoustic-velocity support substrate and the piezoelectric layer in the thickness direction. The high-acoustic-velocity support substrate includes a base region and a surface region disposed nearer to the low-acoustic-velocity film than the base region in the thickness direction and whose crystal quality is worse than that of the base region. The surface region includes first and second layers disposed nearer to the base region than the first layer in the thickness direction and whose crystal quality is better than that of the first layer.

Surface acoustic wave (SAW) filter packages employing an enhanced thermally conductive cavity frame for heat dissipation, and related fabrication methods are disclosed. The SAW filter package also includes a cavity frame comprising a perimeter structure and a cavity inside the perimeter structure coupled to a substrate of a piezoelectric material that contains interdigital transducers (IDTs). A cap substrate is disposed on the perimeter structure of the cavity frame to enclose an air cavity inside the perimeter structure between a substrate and the cap substrate. In exemplary aspects, to effectively dissipate heat generated in the SAW filter package to maintain the desired performance of the SAW filter, the cavity frame is comprised of a material that has an enhanced thermal conductivity. The heat generated in the SAW filter package can more effectively be dissipated, particularly at edges and corners of the cavity frame where hot spots can particularly occur.