Acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern formed is formed on the front surface of the piezoelectric plate, including an interdigital transducer (IDT) with interleaved fingers of the IDT on the diaphragm. The substrate and the piezoelectric plate are the same material.

The present disclosure relates to a method for fabricating a laterally excited shear mode acoustic resonator. The method includes: providing a piezoelectric layer including monocrystalline lithium niobate and/or monocrystalline lithium tantalate; forming an acoustic mirror on a first surface of the piezoelectric layer; the acoustic mirror including at least one first acoustic reflection layer and at least one second acoustic reflection layer, the first acoustic reflection layers and the second acoustic reflection layers being alternately superimposed, and acoustic impedance of each of the first acoustic reflection layers being less than that of each of the second acoustic reflection layers; bonding a bearing wafer on a first surface of the acoustic mirror; and forming an electrode unit and a lateral reflector on a second surface of the piezoelectric layer.

A process for fabricating a micro-electro-mechanical system, includes the following steps: production of a stack on the surface of a temporary substrate so as to produce a first assembly, comprising: at least depositing a piezoelectric material or a ferroelectric material to produce a layer of piezoelectric material or of ferroelectric material; producing a first bonding layer; production of a second assembly comprising at least producing a second bonding layer on the surface of a host substrate; production of at least one acoustic isolation structure in at least one of the two assemblies; production of at least one electrode level containing one or more electrodes in at least one of the two assemblies; bonding the two assemblies via the two bonding layers, before or after the production of the at least one electrode level in at least one of the two assemblies; removing the temporary substrate.

An acoustic wave device includes a support substrate, a piezoelectric layer overlapping the support substrate viewed in a first direction, a functional electrode on at least a first main surface of the piezoelectric layer, and a wiring electrode connected to the functional electrode. A space is provided on a second main surface side opposite to the first main surface of the piezoelectric layer. The space is covered with the piezoelectric layer, the wiring electrode covers a portion of the functional electrode, and an air gap or an insulating film is provided between the functional electrode and the wiring electrode in a region where the functional electrode is covered with the wiring electrode.

An acoustic wave device includes a support substrate, an inorganic film over the support substrate, a piezoelectric layer over the inorganic film, and an electrode over the piezoelectric layer. A portion of the support substrate includes a hollow that overlaps at least a portion of the electrode in a thickness direction of the support substrate. An inner wall of the inorganic film is located farther from the hollow than a location on an inner wall of the support substrate, the location being closest to the piezoelectric layer, the inner wall of the support substrate defining the hollow.

A bulk-acoustic wave resonator may include: a substrate; a resonator unit including a first electrode disposed on the substrate, a piezoelectric layer disposed on the first electrode, and a second electrode disposed on the piezoelectric layer; and a protective layer disposed on a surface of the resonator unit. The protective layer is formed of a diamond film, and a grain size of the diamond film is 50 nm or more.

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.

A microwave dielectric component (100) comprises a microwave dielectric substrate (101) and a metal layer, the metal layer being bonded to a surface of the microwave dielectric substrate (101). The metal layer comprises a conductive seed layer and a metal thickening layer (105). The conductive seed layer comprises an ion implantation layer (103) implanted into the surface of the microwave dielectric substrate (101) and a plasma deposition layer (104) adhered on the ion implantation layer (103). The metal thickening layer (105) is adhered on the plasma deposition layer (104). A manufacturing method of the microwave dielectric component (100) is further disclosed.

An acoustic wave device includes a support substrate, a piezoelectric layer, and a functional electrode. As seen in a first direction of the support substrate, the piezoelectric layer overlaps the support substrate. The functional electrode extends over a first major surface of the piezoelectric layer. A space is opposite to the first major surface of the piezoelectric layer and at or adjacent to a second major surface of the piezoelectric layer. In the first direction, the functional electrode extends over an overlap region that overlaps the space, and a non-overlap region that does not overlap the space. In the non-overlap region, at least one of an insulating film and a void is located between the functional electrode and the piezoelectric layer.

Provided is an acoustic resonator in a transverse excitation shear mode. The acoustic resonator comprises: an acoustic mirror (120), which comprises at least one first acoustic reflecting layer (121, 123, 125) and at least one second acoustic reflecting layer (122, 124), wherein the acoustic impedance of each first acoustic reflecting layer is less than that of each second acoustic reflecting layer; a piezoelectric layer (130), which is arranged on the acoustic mirror, and which comprises lithium niobate of a single crystal material and/or lithium tantalate of a single crystal material; electrode units (142, 143, 144), which are arranged on the piezoelectric layer (130) and are used for forming an electric field; and transverse reflectors (152, 154), which are arranged on the piezoelectric layer, are used for transversely reflecting acoustic waves, and can have a high electromechanical coupling coefficient and a high Q value at a frequency greater than 3 GHz.