An acoustic wave filter provided herein comprises a plurality of series resonators, and a plurality of shunt resonators disposed between the series resonators and a ground, at least one shunt resonator including a substrate, a pair of IDT electrodes disposed on the substrate, each of the IDT electrodes including a bus bar and a plurality of fingers extending from the bus bar, the plurality of fingers of the pair of IDT electrodes including a first group of fingers located at a center region of the pair of IDT electrodes and a second group of fingers located at edge regions on both sides of the center region, the first group of fingers having an average pitch distance shorter than an average pitch distance of the second group of fingers to improve a response at a rejection band of the acoustic wave filter.

A radio frequency duplexer comprises a transmit filter including a first plurality of acoustic wave resonators, and a receive filter including a second plurality of acoustic wave resonators. The transmit filter exhibits a transmit insertion loss curve that partially overlaps with a receive insertion loss curve of the receive filter, a frequency range of the overlap of the transmit insertion loss curve and receive insertion loss curve defining a frequency range of crossover of the duplexer. At least one of the first plurality of acoustic wave resonators or the second plurality of acoustic wave resonators include a structure configured to generate a spurious signal at a frequency within the frequency range of the crossover to reduce an amplitude of an interference signal within the frequency range of the crossover.

An acoustic wave element includes an IDT electrode including electrode fingers, a first substrate on an upper surface of which the IDT electrode is located, which has a thickness of less than 2 times a repetition interval of the electrode fingers and is configured by a piezoelectric crystal, a second substrate bonded to a lower surface of the first substrate, and configured by an Si single crystal having a plane orientation of a (100) plane or (110) plane or a plane equal to them, in which substrate a crystal axis of the Si single crystal parallel to a substrate surface of Si single crystal is inclined at any angle of 25° to 65°, 115° to 155°, 205° to 245°, and 295° to 345° relative to a direction of propagation of an acoustic wave when viewed from the upper surface of the superposed first substrate.

An improved SAW (SAWR) resonator having an improved power durability and heat resistance and a protection to prevent device failure is provided. The SAW resonator has a carrier substrate (S) and an electrode structure (ES, EF) on a piezoelectric material (PM, PL). Further, the resonator has a shunt path (PCPP) parallel to the electrode structure and provided to enable an RF signal to bypass the electrode structure. The shunt path has a temperature dependent conductance with negative temperature coefficient of resistance.

A surface acoustic wave (SAW) resonator comprises a plurality of interdigital transducer (IDT) electrodes disposed on a multilayer piezoelectric substrate including a layer of piezoelectric material having a lower surface bonded to an upper surface of a layer of a dielectric material. The dielectric material has a lower surface bonded to an upper surface of a carrier substrate. The plurality of IDT electrodes include an upper layer and a lower layer. The upper layer is formed of a material having a higher conductivity than the lower layer. The lower layer is formed of a material having a higher density than the upper layer to provide for reduction in size of the SAW resonator.

An acoustic wave resonator includes a support substrate, a piezoelectric layer that is disposed on the support substrate and is a rotated Y-cut X-propagation lithium tantalate of which a cut angle is within a range of greater than 50° and less than 150°, and a pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the comb-shaped electrodes including a plurality of electrode fingers, an average pitch of the electrode fingers of one of the comb-shaped electrodes being equal to or greater than ½ of a thickness of the piezoelectric layer.

An acoustic wave device that includes a spinel layer, a piezoelectric layer and an interdigital transducer electrode on the piezoelectric layer is disclosed. The piezoelectric layer is disposed between the interdigital transducer electrode and the spinel layer. The acoustic wave device is configured to generate an acoustic wave having a wavelength of λ. The piezoelectric layer can have a thickness than is less than A. In some embodiments, the acoustic wave device can include a temperature compensating layer that is disposed between the piezoelectric layer and the spinel layer.

An acoustic wave device includes a support substrate, a quartz-crystal layer provided directly or indirectly on the support substrate, a piezoelectric layer on the quartz-crystal layer, and an IDT electrode on the piezoelectric layer. When λ represents a wavelength defined by an electrode finger pitch of the IDT electrode, a thickness of the quartz-crystal layer is about 0.2λ or more and about 0.4λ or less, and the piezoelectric layer has a thickness smaller than the thickness of the quartz-crystal layer.

An acoustic wave device includes a silicon substrate, a piezoelectric layer, and an IDT electrode. Each of the silicon substrate and the piezoelectric layer includes first and second opposed main surfaces. The IDT electrode is on the first main surface of the piezoelectric layer, and includes first and second electrode fingers. When a wavelength of an acoustic wave determined by an electrode finger pitch of the IDT electrode is denoted as λ, a distance between the first main surface of the silicon substrate and the second main surface of the piezoelectric layer in a thickness direction of the silicon substrate is less than about 0.84λ. The first main surface of the silicon substrate is rougher than the first main surface of the piezoelectric layer.

An acoustic wave device includes a support substrate, a piezoelectric layer, and an IDT electrode. The support substrate is made of quartz. The piezoelectric layer is on the support substrate and is made of LiTaO.sub.3. The IDT electrode is on the piezoelectric layer and includes electrode fingers. The IDT electrode is on a positive surface side of the piezoelectric layer. The cut angle of the piezoelectric layer is equal to or less than about 49° Y.