A lithium tantalate single crystal substrate for a surface acoustic wave device that is a rotated Y-cut LiTaO3 substrate whose crystal orientation has a Y-cut angle of not smaller than 36° and not larger than 49° and which has such a Li concentration profile after diffusion of Li into the substrate from the surface thereof that the Li concentration at the surface of the substrate differs from that inside the substrate. A shear vertical type elastic wave whose main components are vibrations in the thickness direction and in the propagation direction and which is among those elastic waves which propagate in the X axis direction within the surface of this LiTaO3 substrate has an acoustic velocity of not lower than 3140 m/s and not higher than 3200 m/s.

A surface acoustic wave device includes a piezoelectric substrate, an interdigital transducer (IDT) electrode on the substrate, a cover over the substrate and IDT electrode, and hollow spaces between the IDT electrode and the cover. The hollow spaces are defined by partition supports between the substrate and the cover. The partition supports include a first and second partition supports extending in a first direction without contacting each other. The first and second partition supports each include first and second ends along the first direction. The first and second direction perpendicular to the first direction. The first end of the first partition support is closer to an outer periphery of the substrate than is the second end, and the first end of the second partition support is farther away from the outer periphery than is the second end.

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.

Certain aspects of the present disclosure provide a surface acoustic wave (SAW) device with one or more intermediate layers for reduced self-heating and methods for fabricating such a SAW device. One example SAW device generally includes a piezoelectric layer and an interdigital transducer (IDT) disposed above the piezoelectric layer. The IDT generally includes a first electrode having a first busbar and a first plurality of fingers. The first electrode generally includes a first copper layer disposed above the piezoelectric layer, a first intermediate layer disposed above the first copper layer, the first intermediate layer comprising a different material than the first copper layer, and a second copper layer disposed above the first intermediate layer.

A method of making an electronics package with a multi-layer piezoelectric substrate includes bonding a piezoelectric layer over a substrate. The method also includes applying a polyimide layer over an outer boundary of the piezoelectric layer so that the polyimide layer is interposed between the piezoelectric layer and a metal portion (e.g., of copper (Cu)) to inhibit (e.g., prevent) stresses from the metal layer damaging the piezoelectric layer.

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.

The multiplexer includes a plurality of IDT electrodes on a substrate, an insulating cover located on the substrate so as to configure one or more spaces above the plurality of IDT electrodes, an antenna terminal, transmission terminal, and reception terminal which are all located on the substrate and pass through the cover, and a reinforcing layer which is located on the cover and is made of metal. By the plurality of IDT electrodes, a transmission filter located in a signal path connecting the antenna terminal and the transmission terminal and a receiving filter located in a signal path connecting the antenna terminal and the reception terminal. The reinforcing layer includes a first area part facing the transmission filter and a second area part which faces the receiving filter and is separated from the first area part.

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 substrate, an IDT electrode, a spacer layer, a cover, and a protective layer. The spacer layer is provided on the substrate and surrounds the IDT electrode. The cover is provided on the spacer layer, is spaced apart from the IDT electrode, and includes a first main surface adjacent to the spacer layer and a second main surface facing the first main surface. The protective layer includes a third main surface contacting the second main surface, a fourth main surface facing the third main surface, and a side surface connected to the fourth main surface. In at least portion of the side surface of the protective layer, a portion including an intersection line between the side surface and the fourth main surface is located farther inward than an outer edge of the substrate in plan view in the thickness direction of the substrate.

An elastic wave device includes a piezoelectric film made of lithium niobate or lithium tantalate, and a first electrode finger and a second electrode finger opposing each other in a direction intersecting a thickness direction of the piezoelectric film. When an average thickness of the piezoelectric film is d and a distance between centers of the first electrode finger and the second electrode finger is p, d/p is about 0.5 or less. The first electrode finger and the second electrode finger are connected to the first and second bus bars, respectively. The first and second bus bars include corner portions. At least one of corner portions of the first and second bus bars is outside a cavity portion when viewed in plan view.