An acoustic wave device includes a support substrate, a piezoelectric layer provided over the support substrate, comb-shaped electrodes disposed on the piezoelectric layer, each of the comb-shaped electrodes including electrode fingers exciting an acoustic wave, a temperature compensation film interposed between the support substrate and the piezoelectric layer and having a temperature coefficient of an elastic constant opposite in sign to that of the piezoelectric layer, a boundary layer interposed between the support substrate and the temperature compensation film, an acoustic velocity of a bulk wave propagating through the boundary layer being higher than an acoustic velocity of a bulk wave propagating through the temperature compensation film and being lower than an acoustic velocity of a bulk wave propagating through the support substrate, and an intermediate layer interposed between the support substrate and the boundary layer and having a Q factor less than a Q factor of the boundary layer.

An elastic wave device includes a first piezoelectric substrate including a first principal surface and a second principal surface, a second piezoelectric substrate including a first principal surface and a second principal surface and with a greater thickness than that of the first piezoelectric substrate, and ground terminals located on the second principal surface of the first piezoelectric substrate. The first principal surface of the first piezoelectric substrate and the first principal surface of the second piezoelectric substrate are joined to face each other. On the first principal surface of the first piezoelectric substrate, a first elastic wave filter is located. On the first principal surface of the second piezoelectric substrate, a second elastic wave filter is located. The out-of-band attenuation of the first elastic wave filter is greater than the out-of-band attenuation of the second elastic wave filter.

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 ladder filter defines a transmission filter and has a structure such that a resonator located closest to an input terminal is a parallel-arm resonator, and the parallel-arm resonator located closest to the input terminal includes a plurality of division resonators connected in parallel. At least one division resonator has a resonant frequency and an anti-resonant frequency that are located outside a passband of the ladder filter, and the remaining division resonators and parallel-arm resonators each have an anti-resonant frequency located within the passband.

A surface acoustic wave resonator includes: a piezoelectric substrate; a plurality of metal structures formed on a top surface of the piezoelectric substrate to have a negative profile; and a temperature compensation layer covering the top surface of the piezoelectric substrate and the plurality of metal structures. The surface acoustic wave resonator according to an embodiment of the present invention has a frequency characteristic insensitive to change of profile and has an effect of having a high semi-resonance Q value characteristic.

An acoustic wave filter includes: a series-arm resonator disposed on a path that connects input/output terminals; and a parallel-arm circuit connected to a node on the path and a ground. The parallel-arm circuit includes a parallel-arm resonator and a capacitor connected in parallel to each other. The capacitor includes a comb-shaped electrode that includes electrode fingers. A frequency at which impedance of the capacitor has a local maximum value is located outside a passband of the acoustic wave filter. The comb-shaped electrode has at least two different electrode finger pitches or at least two different electrode finger duty ratios.

A multi-resonator filter has a signal input terminal, a signal output terminal, and a plurality of resonator components. The plurality of resonator components include an input resonator component coupled to the signal input terminal, an output resonator component coupled to the signal output terminal, and at least one intermediate resonator component coupled between the input resonator component and the output resonator component. The input resonator component, output resonator component and the at least one intermediate resonator component are arranged in a sequence to define a signal path between the signal input terminal and the signal output terminal. The at least one intermediate resonator component includes at least one multiple resonator component, where each multiple resonator component includes a pair of individual resonators coupled in parallel where each individual resonator in a given pair of individual resonators has the same resonant frequency.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a piezoelectric plate having front and back surfaces and an interdigital transducer (IDT). The IDT has a first pitch/mark zone with interleaved fingers having a pitch equal to a first pitch value P.sub.1 and a mark equal to a first mark value M.sub.1, and a second pitch/mark zone with interleaved fingers having a pitch equal to a second pitch value P.sub.2 and a mark equal to a second mark value M.sub.2. A radio frequency signal applied to the IDT causes excitation of a same shear primary acoustic mode by both the first pitch/mark zone and the second pitch/mark zone. P1, M1, P2, and M2, are selected such that an amplitude of spurious modes is reduced as compared to a device having a same primary acoustic mode and a single pitch/mark zone.

A micro-acoustic RF filter comprises first and second ports (101, 102). First and a second signal paths (120, 110) are coupled between the first and second ports and include a corresponding resonator (111, 121). The resonator of at least one of the signal paths is a micro-acoustic resonator. One of the signal paths includes also a phase shifter (232) serially connected with the resonator (111). The micro-acoustic RF filter achieves a broad passband determined by the resonance frequencies of the micro-acoustic resonators. The filter allows flexible adaption of the passband and stopband performance.

Stack assembly for radio-frequency applications. In some embodiments, a radio-frequency (RF) module can include a packaging substrate configured to receive a plurality of components, and an electro-acoustic device mounted on the packaging substrate. The RF module can further include a die having an integrated circuit and mounted over the electro-acoustic device to form a stack assembly. The electro-acoustic device can be, for example, a filter device such as a surface acoustic wave filter. The die can be, for example an amplifier die such as a low-noise amplifier implemented on a silicon die.