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.

There is provided a laminated substrate having a piezoelectric film, including: a substrate; and a piezoelectric film provided on the substrate interposing a base film, wherein the piezoelectric film has an alkali niobium oxide based perovskite structure represented by a composition formula of (K.sub.1-xNa.sub.x)NbO.sub.3 (0<x<1) and preferentially oriented in (001) plane direction, and a sound speed of the piezoelectric film is 5100 m/s or more.

An acoustic wave device includes a support substrate, a piezoelectric layer on the support substrate, and a functional element on the piezoelectric layer. The support substrate and the piezoelectric layer each have a rectangular or substantially rectangular shape in plan view from a direction normal to the support substrate. At least one corner portion of the piezoelectric layer has a curved shape or a polygonal shape.

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.

A ceramic substrate is formed of polycrystalline ceramic and has a supporting main surface. At the supporting main surface of the ceramic substrate, the mean of grain sizes of the polycrystalline ceramic is 15 μm or more and less than 40 μm and the standard deviation of the grain sizes is less than 1.5 times the mean.

A bonded body includes a supporting substrate, silicon oxide layer provided on the supporting substrate, and a piezoelectric material substrate provided on the silicon oxide layer and composed of a material selected from the group consisting of lithium niobate, lithium tantalate and lithium niobate-lithium tantalite. A nitrogen concentration at an interface between the piezoelectric material substrate and silicon oxide layer is higher than a nitrogen concentration at an interface between the silicon oxide layer and the supporting substrate.

A method for fabricating a surface acoustic wave (SAW) device includes the steps of forming a first dielectric layer on a substrate, forming a piezoelectric layer on the first dielectric layer, forming a second dielectric layer on the piezoelectric layer, performing a photo-etching process to remove the second dielectric layer for forming a recess in the second dielectric layer, forming a metal layer in the recess, and then performing a planarizing process to remove the metal layer for forming an electrode in the recess.

A fabrication method of a surface acoustic wave (SAW) filter includes obtaining a piezoelectric substrate, forming a first interdigital transducer (IDT) on a first portion of the piezoelectric substrate, forming a first pad metal layer on the first IDT, forming a first dielectric layer on the first portion of the piezoelectric substrate, covering the first IDT and the first pad metal layer, forming a trench in the first dielectric layer, forming a second dielectric layer on the first dielectric layer, forming a third dielectric layer on the second dielectric layer, removing a second portion of the piezoelectric substrate to obtain a piezoelectric layer, forming a second IDT on the piezoelectric layer, and etching and releasing a portion of the first dielectric layer surrounded by the trench to form a cavity.

A method for fabricating a surface acoustic wave (SAW) device includes the steps of forming a buffer layer on a substrate, forming a high velocity layer on the buffer layer, forming a medium velocity layer on the high velocity layer, forming a low velocity layer on the medium velocity layer, forming a piezoelectric layer on the low velocity layer, and forming an electrode on the piezoelectric layer. Preferably, the buffer layer includes silicon oxide, the high velocity layer includes graphene, the medium velocity layer includes silicon oxynitride, and the low velocity layer includes titanium oxide.

Provided is a method of manufacturing a composite substrate equipped with a piezoelectric single-crystal film having good film-thickness uniformity and not causing deterioration in properties even if ion implantation is performed. The method of manufacturing a composite substrate 10 equipped with a piezoelectric single-crystal film 11 according to the present invention includes the steps of: (a) subjecting a piezoelectric single-crystal substrate 1 made of lithium tantalate or lithium niobate to ion implantation treatment to form an ion implantation layer 11, (c) bonding the surface of the piezoelectric single-crystal substrate 1 having the ion implantation layer 11 thereon to a temporary bonding substrate 2, (d) separating the piezoelectric single-crystal substrate 1 into the ion implantation layer 11 and the remaining portion of the substrate to form a piezoelectric single-crystal film 11 on the temporary bonding substrate 2, (f) bonding a supporting substrate 3 to the surface of the piezoelectric single-crystal film 11 opposite to a bonded surface of the temporary bonding substrate, and (g) separating the temporary bonding substrate from the piezoelectric single-crystal film 11.