An acoustic wave device includes an IDT electrode on a piezoelectric substrate and reflector electrodes on both sides of the IDT electrode in an acoustic wave propagation direction and each including electrode fingers with gaps therebetween, and first dielectric films between the reflector electrodes and the piezoelectric substrate in regions where the electrode fingers and the gaps of the reflector electrodes are provided.

An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity V.sub.si=(V.sub.1).sup.1/2 of propagation through silicon or higher than the acoustic velocity V.sub.si, where V.sub.si is specified by V.sub.1 among solutions V.sub.1, V.sub.2, and V.sub.3 with respect to x derived from Ax.sup.3+Bx.sup.2+Cx+D=0.

A piezoelectric device includes a support substrate, an intermediate layer on the support substrate, a piezoelectric layer on the intermediate layer, a functional element on the piezoelectric layer, an insulation layer, and a wiring electrode. The insulation layer is on the support substrate and in contact with the intermediate layer and the piezoelectric layer. The wiring electrode extends from a top of the insulation layer to a top of the piezoelectric layer and is connected to the functional element. The insulation layer includes first and second regions. The first region is thinner than a thickness of the multilayer body. The second region connects the first region and the multilayer body, and includes a portion slanted from the first region toward an upper surface of the piezoelectric layer. The second region of the insulation layer does not extend to the top of the piezoelectric layer.

Aspects of this disclosure relate to an acoustic wave filter that includes acoustic wave resonators arranged to filter a radio frequency signal. The acoustic wave resonators include a first acoustic wave resonator. The acoustic wave filter includes a circuit element in parallel with the first acoustic wave resonator in a stage of the acoustic wave filter. The circuit element and the first acoustic wave resonator have different resonant frequencies. The circuit element can reduce an impact of bulk mode of the first acoustic wave resonator on insertion loss of the acoustic wave filter. The first acoustic wave resonator can be a surface acoustic wave resonator in certain embodiments. The circuit element can be a second acoustic wave resonator or a capacitor, for example.

Aspects of this disclosure relate to an acoustic wave filter that includes acoustic wave resonators arranged to filter a radio frequency signal. The acoustic wave resonators include a first acoustic wave resonator. The acoustic wave filter includes a circuit element in parallel with the first acoustic wave resonator in a stage of the acoustic wave filter. The circuit element and the first acoustic wave resonator have different resonant frequencies. The circuit element can reduce an impact of bulk mode of the first acoustic wave resonator on insertion loss of the acoustic wave filter. The first acoustic wave resonator can be a surface acoustic wave resonator in certain embodiments. The circuit element can be a second acoustic wave resonator or a capacitor, for example.

An acoustic wave device, a method of manufacture of the same, and a radio frequency filter including the same. The acoustic wave device comprises a multilayer piezoelectric substrate (MPS) including a layer of piezoelectric material having a lower surface disposed on an upper surface of a layer of a dielectric material having a lower surface disposed on an upper surface of a carrier substrate. An interdigital transducer (IDT) is disposed on the multilayer piezoelectric substrate and includes an active region configured to generate an acoustic wave. First and second high impedance portions are included within the multilayer piezoelectric substrate, the first and second high impedance portions each positioned outside the active region of the interdigital transducer and extending in the direction of propagation of the acoustic wave to be generated by the interdigital transducer. The first and second high impedance portions reduce side leakage and suppress transverse modes.

An acoustic wave device includes an acoustic wave element substrate, filter electrodes on a first surface of the acoustic wave element substrate, a first insulator layer covering a second surface of the acoustic wave element substrate, and a second insulator layer laminated on the first insulator layer and sandwiching the first insulator layer between the second insulator layer and the acoustic wave element substrate. The products of propagation speeds of an acoustic wave in those layers and densities of those layers satisfy a predetermined relationship.

An acoustic wave device includes an element substrate having piezoelectricity, a functional electrode on a first main surface of the element substrate, an extended wiring line electrically connected to the functional electrode and extending from the first main surface to a side surface of the element substrate, an external terminal electrically connected to the extended wiring line and on a second main surface of the element substrate, a first resin portion to seal the acoustic wave device, and a second resin portion at least between the extended wiring line on the side surface and the first resin portion. The second resin portion has a lower Young's modulus than the first resin portion.

An acoustic wave device includes a silicon support substrate that includes first and second main surfaces opposing each other, a piezoelectric structure provided on the first main surface and including the piezoelectric layer, an IDT electrode provided on the piezoelectric layer, a support layer provided on the first main surface of the silicon support substrate and surrounding the piezoelectric layer, a cover layer provided on the support layer, a through-via electrode that extending through the silicon support substrate and the piezoelectric structure, and a first wiring electrode connected to the through-via electrode and electrically connected to the IDT electrode. The piezoelectric structure includes at least one layer having an insulating property, the at least one layer including the piezoelectric layer. The first wiring electrode is provided on the layer having an insulating property in the piezoelectric structure.

An elastic wave device includes a piezoelectric film, a high acoustic velocity member, a low acoustic velocity film located between the piezoelectric film and the high acoustic velocity member and through which an elastic wave propagates at a lower acoustic velocity than an elastic wave that propagates through the piezoelectric film, and an interdigital transducer electrode including electrode fingers separated from each other and disposed side by side in a first direction. At least one of the electrode fingers includes a first metal layer including first and second main body portions. A recessed portion is located in a central region in the first direction of the electrode finger and is recessed in the thickness direction of the piezoelectric film. A protrusion portion protrudes from at least a portion of the first main body portion in the first direction.