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 surface acoustic wave (SAW) filter includes a filter wafer including: a first substrate; and an interdigital transducer (IDT) disposed on the first substrate, the IDT including a first input and output end, a second input and output end, and an interdigital portion. The SAW filter also includes a dielectric layer disposed on the filter wafer, covering the first input and output end and the second input and output end of the IDT and exposing the interdigital portion; a passivation layer disposed on the dielectric layer; a bonding layer disposed on the passivation layer; a second substrate bonded to the filter wafer via the bonding layer; and a cavity enclosed by the second substrate and the bonding layer.

An interdigital transducer for a surface-acoustic-wave resonator includes a conductive grid and a plurality of practical electrodes. The conductive grid includes a bus bar, a plurality of dummy electrodes and a conductive bar. The bus bar has a signal transmission terminal, and is disposed on a first side of the first conductive grid. The plurality of dummy electrodes directly extend from the bus bar. The conductive bar is disposed on a second side of the first conductive grid, and is opposite to the bus bar. Each of the plurality of practical electrodes extends from the conductive bar.

An acoustic wave device includes a piezoelectric substrate and an IDT electrode including electrode fingers, a first layer on the piezoelectric substrate, and a second layer on the first layer and including Cu as a main component. The first layer includes a first principal surface on a side closest to the piezoelectric substrate and a second principal surface in contact with the second layer. The second layer includes a third principal surface in contact with the first layer, a fourth principal surface opposite to the third principal surface, and a side surface connected to the third and fourth principal surfaces. The IDT electrode includes a barrier layer on the side surface of the second layer. A boundary between the side surface of the second layer and the barrier layer is on the second principal surface of the first layer, and the barrier layer does not reach the piezoelectric substrate.

An acoustic wave device includes a piezoelectric substrate and an IDT electrode including electrode fingers, a barrier layer on the piezoelectric substrate, and a first layer on the barrier layer, and including Cu as a main component. The first layer includes a first principal surface on a side closest to the piezoelectric substrate, a second principal surface opposite to the first principal surface, and a side surface connected to the first principal surface and the second principal surface. The barrier layer covers the first principal surface 5a and the side surface of the first layer. A thickness of a portion of the barrier layer covering the first principal surface of the first layer is smaller than a thickness of a portion of the barrier layer covering the side surface of the first layer.

A surface acoustic wave device includes a piezoelectric substrate formed from a Ca.sub.3Ta(Ga.sub.1-xAl.sub.x).sub.3Si.sub.2O.sub.14 single crystal, and an interdigital electrode formed on the surface of the piezoelectric substrate and formed from Al. The interdigital electrode is configured to generate a Love-wave-type SH wave on the surface of the piezoelectric substrate. A normalized film thickness obtained by dividing the film thickness of the interdigital electrode by the wavelength of the Love-wave-type SH wave is 0.16 or less.

In an elastic wave device, an IDT electrode is provided on a piezoelectric substrate and a first silicon oxide film covers the IDT electrode. A high-acoustic-velocity dielectric film covers the first silicon oxide film. A second silicon oxide film is provided on the high-acoustic-velocity dielectric film. The piezoelectric substrate is made of lithium niobate. The high-acoustic-velocity dielectric film propagates longitudinal waves at an acoustic velocity higher than an acoustic velocity of longitudinal waves propagating through the first silicon oxide film. The high-acoustic-velocity dielectric film is provided at a distance of about (t1+t2)×0.42 or less from a first main surface of the piezoelectric substrate in a thickness direction of the piezoelectric substrate.

Surface acoustic wave resonators are disclosed. In certain embodiments, a surface acoustic wave resonator can include a high impedance layer, a piezoelectric layer over the high impedance layer, an interdigital transducer electrode over the piezoelectric layer, and a low impedance layer between the high impedance layer and the piezoelectric layer. An acoustic impedance of the high impedance layer is greater than an acoustic impedance of the piezoelectric layer. An acoustic impedance of the low impedance layer is lower than the acoustic impedance of the high impedance layer. The piezoelectric layer can have a cut angle in a range from 115° to 135°. The surface acoustic wave resonator is configured to generate a Rayleigh mode surface acoustic wave having a wavelength of λ.

An acoustic wave device can include a substrate, a piezoelectric layer, a first electrode that includes a first bus bar and a first plurality of fingers extending from the first bus bar, and a second electrode that includes a second bus bar and a second plurality of fingers extending from the second bus bar. The second plurality of fingers can be interdigitated with the first plurality of fingers. The acoustic wave device can include a raised frame structure. The raised frame structure can be configured to suppress a transverse mode. The fingers can have widths that are greater than the distances between the fingers. The acoustic wave device can include a bus bar that includes a main section and a secondary section that are electrically connected by gap lines, which can have smaller width than the fingers. The acoustic wave device can include dummy fingers.

An acoustic wave device includes a silicon substrate, a first high-acoustic-velocity film on the silicon substrate, a first low-acoustic-velocity film on the first high-acoustic-velocity film, a second low-acoustic-velocity film on the first low-acoustic-velocity film, a second high-acoustic-velocity film on the second low-acoustic-velocity film, a piezoelectric film on the second high-acoustic-velocity film, and an IDT electrode on the piezoelectric film. Acoustic velocities of bulk waves propagating through the first and second high-acoustic-velocity films are higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric film. Acoustic velocities of bulk waves propagating through the first and second low-acoustic-velocity films are lower than an acoustic velocity of a bulk wave propagating through the piezoelectric film. Materials of the first and second low-acoustic-velocity films are different from each other.