An acoustic wave device includes an energy confinement layer, a piezoelectric layer made of Y-cut X-propagation lithium tantalate having a cut angle in a range from about −10° to about 65°, and an IDT electrode. Electrode fingers of the IDT electrode include an Al metal layer and a high acoustic impedance metal layer having a Young's modulus equal to or more than about 200 GPa and an acoustic impedance higher than Al. The high acoustic impedance metal layer is closer to the piezoelectric layer than the Al metal layer. A wavelength specific film thickness t.sub.LT of the piezoelectric layer is expressed by t.sub.LT≤1λ. The total of normalized film thicknesses obtained by normalizing the film thickness of each layer of the electrode finger by a density and Young's modulus of the Al metal layer satisfies T≤0.1125t.sub.LT+0.0574.

An acoustic wave device includes: a piezoelectric substrate; and a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the comb-shaped electrodes including a plurality of electrode fingers, side surfaces facing each other of the electrode fingers having a plurality of protrusion portions and a plurality of recessed portions arranged in an extension direction of the electrode fingers, ends of the protrusion portions and the recessed portions narrowing.

An elastic wave device includes a piezoelectric substrate mainly including lithium niobate, an interdigital transducer electrode provided on the piezoelectric substrate, and a dielectric film, provided on the piezoelectric substrate and covering the interdigital transducer electrode, and mainly including silicon oxide. The elastic wave device uses a Rayleigh wave. The interdigital transducer electrode includes main electrode layers that include one or more first main electrode layer made of a metal with a C11.sup.2/C12 ratio greater than the C11.sup.2/C12 ratio of the silicon oxide with regard to the elastic constants C11 and C12. The sum of the thicknesses of the one or more first main electrode layers is about 55% or more based on the thickness of the whole interdigital transducer electrode is about 100%.

An acoustic wave device includes a piezoelectric substrate, and an IDT electrode provided on the piezoelectric substrate. The IDT electrode includes an overlap region where first and second electrode fingers overlap each other in a first direction. The overlap region includes a central region located in a substantially central portion of the overlap region with respect to a second direction. The central region includes a low acoustic velocity portion with an acoustic velocity less than the acoustic velocity in another portion. The overlap region includes first and second low acoustic velocity regions. The first and second low acoustic velocity regions are respectively located on first-and-second-busbar sides from the central region. The IDT electrode includes first and second high acoustic velocity regions. The first and second high acoustic velocity regions are respectively located outside the first and second low acoustic velocity regions with respect to the second direction.

Aspects of this disclosure relate to an acoustic wave device that includes a multi-layer interdigital transducer electrode. The acoustic wave device includes a piezoelectric layer and an interdigital transducer electrode on the piezoelectric layer. The interdigital transducer electrode includes a first interdigital transducer electrode layer positioned between a second interdigital transducer electrode layer and the piezoelectric layer. The second interdigital transducer electrode layer can include aluminum and having a thickness of at least 200 nanometers. The acoustic wave device can include a temperature compensation layer arranged such that the interdigital transducer electrode is positioned between the piezoelectric layer and at least a portion of the temperature compensation layer. Related filters, modules, wireless communication devices, and methods are disclosed.

An acoustic wave element includes a piezoelectric substrate, an IDT electrode on the piezoelectric substrate, and a reflector. The IDT electrode includes plural electrode fingers, and the reflector includes plural reflector electrode fingers. In a case where IRGAP is an IDT-reflector gap that is a distance between a center of the electrode finger located closest to the reflector and a center of the reflector electrode finger located closest to the IDT electrode, and λ.sub.REF is a reflector wave length that is twice a repetition pitch of the reflector electrode fingers, a ratio of about 0.25≤IRGAP/λ.sub.REF≤about 0.44 is satisfied, and the reflector wave length is longer than an IDT wave length that is a repetition pitch of the electrode fingers.

A bandpass acoustic wave filter device includes an IDT electrode and a dielectric film disposed on a piezoelectric substrate including a LiNbO.sub.3 layer, and an acoustic wave resonator is defined by the IDT electrode. The acoustic wave resonator utilizes the Rayleigh wave, and a response of an SH wave excited by the acoustic wave resonator is outside a pass band of the acoustic wave filter device.

An acoustic wave device is disclosed. the acoustic wave device is configured to generate a wave having a wavelength of L. The acoustic wave device includes a piezoelectric layer a first layer of an interdigital transducer electrode over the piezoelectric layer, and a second layer of the interdigital transducer electrode over the first layer. The first layer has a material with a first mass density of ρ. The first mass density of ρ is greater than 5000 kg/m.sup.3. The first layer has a thickness of t1 less than 0.04 L. The first layer can have the thickness of t1 in a range between 0.0025 L(10220/ρ) and 0.04 L(10220/ρ). The second layer has a material with a second mass density that is smaller than the first mass density.

An acoustic wave device is disclosed. The acoustic wave device can be configured to generate a wave having a wavelength of L. The acoustic wave device can include a piezoelectric layer, a first layer of an interdigital transducer electrode over the piezoelectric layer, and a second layer of the interdigital transducer over the first layer. The first layer has a first material with a first mass density. The first material has a normalized mechanical loading exchange rate that is normalized by a mechanical loading exchange rate of molybdenum. The first layer has a thickness less than 0.04L multiplied by the normalized mechanical loading exchange rate of the first material. The second layer has a second material with a second mass density smaller than the first mass density.

A temperature coefficient of frequency compensated surface acoustic wave device is provided which includes: a piezoelectric substrate, an interdigital transducer configured to generate a surface acoustic wave in response to an electrical signal and a first temperature compensation layer disposed on the piezoelectric substrate, the interdigital transducer being disposed on the temperature compensation layer.