Embodiments of a Surface Acoustic Wave (SAW) device having a guided SAW structure that provides spurious mode suppression and methods of fabrication thereof are disclosed. In some embodiments, a SAW device includes a non-semiconductor support substrate, a piezoelectric layer on a surface of the non-semiconductor support substrate, and at least one interdigitated transducer on a surface of the piezoelectric layer opposite the non-semiconductor support substrate. A thickness of the piezoelectric layer, a SAW velocity of the piezoelectric layer, and an acoustic velocity of the non-semiconductor support substrate are such that a frequency of spurious modes above a resonance frequency of the SAW device is above a bulk wave cut-off frequency of the SAW device. In this manner, the spurious modes above the resonance frequency of the SAW device are suppressed.

A SAW filter includes a substrate including a piezoelectric substrate, a transmission filter, and an additional resonator. The transmission filter is a ladder-type filter filtering signals from a transmission terminal and outputting the result to an antenna terminal. Further, the transmission filter includes one or more serial resonators and one or more parallel resonators which are connected in a ladder configuration on the piezoelectric substrate. An initial stage resonator is the serial resonator. The additional resonator includes an IDT electrode on the piezoelectric substrate. The IDT electrode is connected to the transmission terminal at a stage before the transmission filter and is connected to any of the one or more GND terminals. In the additional resonator, a resonance frequency and an antiresonance frequency are located outside of a passband of the transmission filter.

A surface acoustic wave (SAW) device includes a substrate; an interdigital transducer (IDT) having lead-out portions and arrays of interdigital electrodes formed on the substrate, wherein the interdigital electrodes includes central portions, end portions, and intermediate portions between the end portions and the lead-out portions, and a thickness of the interdigital electrodes at the end portions is greater than a thickness of the interdigital electrodes at the central portions and the intermediate portions, thereby forming protruding structures at the end portions of the interdigital electrodes; a protective layer formed on the protruding structures at the end portions of the interdigital electrodes; a first temperature compensation layer formed on the protective layer; a second temperature compensation layer formed on the first temperature compensation layer and on the central portions and the intermediate portions of the interdigital electrodes; and a passivation layer formed on the second temperature compensation layer.

An elastic wave device includes a plate-shaped elastic wave element and a resin structure including a high elastic modulus resin portion and low elastic modulus resin portions. The low elastic modulus resin portions are provided in regions of side surfaces of an elastic wave element substrate, which extend from end portions at an IDT electrode formation surface side and do not reach a surface at a side opposite to an IDT electrode formation surface, and a remaining resin portion of a portion of the resin structure, which contacts with the side surfaces of the elastic wave element substrate, is the high elastic modulus resin portion.

An elastic wave device includes an elastic wave element chip, a bump electrically connected to the elastic wave element chip, a package substrate including an electrode bonded to the bump, the elastic wave element chip mounted on the package substrate with the bump, and a sealing resin portion covering the elastic wave element chip on the package substrate. A space surrounded by the elastic wave element chip, the package substrate, and the sealing resin portion is provided. The elastic wave element chip includes a substrate having piezoelectricity, an interdigital transducer electrode, and a pad electrode. A first main surface of the substrate having piezoelectricity includes a first region and a second region closer to a second main surface than the first region. The interdigital transducer electrode is disposed in the first region. The pad electrode is disposed in the second region and bonded to the bump.

A surface acoustic wave resonator (100) comprises a layered substrate including a carrier substrate (110) and a dielectric layer (112) having a low acoustic velocity. Another dielectric layer (122) is disposed on a piezoelectric layer (113) and interdigitated electrodes (131, 132) having an acoustic velocity lower than the acoustic velocity of the carrier substrate (110) and a positive temperature coefficient of frequency.

A high-frequency module includes a semiconductor element, a first insulating layer, an acoustic wave element, a second insulating layer, a first intermediate layer, and a second intermediate layer. The first intermediate layer is interposed between the acoustic wave element and the semiconductor element, and has a thermal conductivity lower than the first and second insulating layers. The second intermediate layer is interposed between the first insulating layer and the second insulating layer, and has a thermal conductivity lower than the first and second insulating layers. A step is provided between a first principal surface of the first insulating layer and one principal surface of the semiconductor element. The distance between first and second principal surfaces of the first insulating layer is greater than the distance between the second principal surface of the first insulating layer and the one principal surface of the semiconductor element.

A piezoelectric composite substrate for SAW devices with small loss is provided. A composite substrate for a surface acoustic wave device according to one embodiment of the present invention has a piezoelectric single crystal thin film, a support substrate, and a first intervening layer between the piezoelectric single crystal thin film and the support substrate. In said composite substrate, the first intervening layer is in contact with the piezoelectric single crystal thin film, and the acoustic velocity of the transverse wave in the first intervening layer is faster than the acoustic velocity of the fast transverse wave in the piezoelectric single crystal thin film.

An acoustic wave device with a bent section is disclosed. The acoustic wave device includes a piezoelectric layer and an interdigital transducer electrode on the piezoelectric layer. The bent section is arranged to create a curvature in a waveguide of the acoustic wave device to suppress a transverse spurious mode of the acoustic wave device.

Aspects of this disclosure relate to a surface acoustic wave filter with an integrated temperature sensor. The integrated temperature sensor can be a resistive thermal device configured as a reflective grating for a surface acoustic wave resonator, for example. A radio frequency system can provide over temperature protection by reducing a power level of a radio frequency signal provided to the surface acoustic wave filter responsive to an indication of temperature provided by the integrated temperature sensor satisfying a threshold.