The present invention relates to a heterostructure, in particular, a piezoelectric structure, comprising a cover layer, in particular, a layer of piezoelectric material, the material of the cover layer having a first coefficient of thermal expansion, assembled to a support substrate, the support substrate having a second coefficient of thermal expansion substantially different from the first coefficient of thermal expansion, at an interface wherein the cover layer comprises at least a recess extending from the interface into the cover layer, and its method of fabrication.

A multiplexer includes acoustic wave filters that are electrically connected to a common connection terminal. In a first transmission-side filter of the acoustic wave filters, a series arm resonator closest to the common connection terminal includes acoustic wave resonators that are electrically connected in series and capacitance elements that are electrically connected between at least one of signal paths electrically connecting the acoustic wave resonators to each other and a reference terminal.

A multiplexer includes a transmission-side filter electrically connected to a common terminal and a transmission input terminal, and a transmission-side filter electrically connected to the common terminal and a transmission input terminal. The transmission-side filter includes a plurality of series arm resonators and a plurality of parallel arm resonators. Capacitance elements are respectively electrically connected in parallel to the series arm resonator and the parallel arm resonator, which are connected most proximately to the common terminal. IDT electrodes of a series arm resonator and a parallel arm resonator connected most proximately to the common terminal do not include a thinning electrode, and others of the series arm resonators and the parallel arm resonators include thinning electrodes.

An acoustic wave device includes a support substrate, a silicon nitride film stacked on the support substrate, a silicon oxide film stacked on the silicon nitride film, a piezoelectric body stacked on the silicon oxide film and made of lithium tantalite, and an IDT electrode provided on one main surface of the piezoelectric body. For a wavelength normalized film thickness of the piezoelectric body, an Euler angle of the piezoelectric body, a wavelength normalized film thickness of the silicon nitride film, a wavelength normalized film thickness of the silicon oxide film, and a wavelength normalized film thickness of the IDT electrode, values are set so that at least one of a response intensity of a first higher order mode, corresponding to the response intensity of a second higher order mode, and of a response intensity of a third higher mode is greater than about −2.4.

An acoustic wave device includes a support substrate made of silicon, a piezoelectric body provided directly or indirectly on the support substrate, the piezoelectric body including a pair of main surfaces facing each other, and an interdigital transducer electrode provided directly or indirectly on at least one of the main surfaces of the piezoelectric body, a wave length that is determined by an electrode finger pitch of the interdigital transducer electrode being λ. An acoustic velocity V.sub.Si=(V.sub.1).sup.1/2 of bulk waves that propagate in the support substrate, which is determined by V.sub.1 out of solutions V.sub.1, V.sub.2, V.sub.3 of x derived from the expression, Ax.sup.3+Bx.sup.2+Cx+D=0, is higher than or equal to about 5500 m/s.

An acoustic wave device includes a multilayer substrate including a reverse-velocity surface, a piezoelectric film, a low acoustic velocity material layer, a high acoustic velocity material layer, and an IDT electrode disposed on the piezoelectric film. In the IDT electrode, gap lengths of a first gap between a tip of each of first electrode fingers and a second busbar and a second gap between a tip of each of second electrode fingers and a first busbar are about 0.23λ or shorter, the gap lengths extending in an extension direction of the first and second electrode fingers.

An acoustic wave filter device includes at least one series arm resonator and a parallel arm resonator. The series arm resonators and the parallel arm resonator are defined by acoustic wave resonators, an interdigital transducer electrode of the series arm resonators is an apodized interdigital transducer electrode subjected to apodization weighting, in the interdigital transducer electrode of the parallel arm resonator, an intersecting portion includes a central region and low acoustic velocity regions provided at both outer side portions of the central portion, an acoustic velocity of an acoustic wave in the low acoustic velocity region is lower than an acoustic velocity of an acoustic wave in the central region, and a high acoustic velocity region where an acoustic velocity of an acoustic wave is higher than that of the low acoustic velocity region is provided at an outer side portion of each of the low acoustic velocity regions.

The present invention relates to a heterostructure, in particular, a piezoelectric structure, comprising a cover layer, in particular, a layer of piezoelectric material, the material of the cover layer having a first coefficient of thermal expansion, assembled to a support substrate, the support substrate having a second coefficient of thermal expansion substantially different from the first coefficient of thermal expansion, at an interface wherein the cover layer comprises at least a recess extending from the interface into the cover layer, and its method of fabrication.

A surface acoustic wave (SAW) resonator is provided with reduced rattling at frequencies lower than the resonance value. The SAW resonator includes an interdigital transducer (IDT) on a piezoelectric substrate. The IDT includes a first set of interdigital electrodes distributed between and parallel to the first end of the IDT and the second end of the IDT and a second set of interdigital electrodes interleaved with the first plurality of interdigital electrodes. A first resonant cavity is formed a predetermined distance from the first end of the IDT, and a second resonant cavity is formed a predetermined distance from the second end of the IDT. Additionally, a radio frequency (RF) filter is provided that includes multiple SAW resonators that include the resonant cavities formed a predetermined distance from the first and second ends of the IDT. This RF filter may provide increased bandwidth and reduced insertion loss.

A filter device that reduces spurious emissions generated in a frequency band 1.2 to 1.4 times greater than a center frequency of a passband of a filter. In one example the filter device includes a first filter connected between a common contact and a first signal contact and having a first passband, and a second filter connected between the common contact and a second signal contact and having a second passband with a center frequency in a range of 1.2 to 1.4 times greater than a center frequency of the first passband. The first filter includes a SAW filter formed on a piezoelectric substrate, a SAW resonator formed on the piezoelectric substrate and connected in series between the common contact and the SAW filter, and a dielectric film covering the SAW filter and SAW resonator, the dielectric film having a reduced thickness in a region corresponding to the SAW resonator.