A substrate for a surface acoustic wave device or bulk acoustic wave device, comprising a support substrate and an piezoelectric layer on the support substrate, wherein the support substrate comprises a semiconductor layer on a stiffening substrate having a coefficient of thermal expansion that is closer to the coefficient of thermal expansion of the material of the piezoelectric layer than that of silicon, the semiconductor layer being arranged between the piezoelectric layer and the stiffening substrate.

An acoustic resonator includes: a resonating unit including a resonating unit including a piezoelectric layer and first and second electrodes disposed on a lower side and an upper side of the piezoelectric layer, respectively; a substrate disposed on a lower side of the resonating unit; a support unit providing a cavity between the substrate and the resonating unit; and an intermediate metal layer separated from the second electrode and disposed in the resonating unit such that at least a portion thereof is surrounded by the piezoelectric layer and the second electrode.

An acoustic resonator includes: a resonating unit including a piezoelectric layer, a first electrode disposed on a lower side of the piezoelectric layer, and a second electrode disposed on an upper side of the piezoelectric layer; a substrate disposed below the resonating unit; a support unit forming a cavity between the substrate and the resonating unit; and a pillar extending through the cavity and connecting the resonating unit to the substrate. The resonating unit further includes a first insertion layer disposed above the pillar.

An acoustic resonator device is formed that reduces a thermal coefficient of expansion mismatch between a piezoelectric plate and a silicon substrate by bonding the front surface of the silicon substrate having a filled and planarized sacrificial tub to a piezoelectric substrate and thinning the silicon substrate by removing material from a back surface. That back surface is then bonded to a handle wafer having a thermal coefficient of expansion (TCE) closer to a TCE of the piezoelectric substrate than a TCE of the silicon substrate and thinning the piezoelectric substrate to a target piezoelectric membrane thickness to form a piezoelectric plate. A conductor pattern is formed on the thinned piezoelectric plate and the sacrificial tub is removed to form a cavity and release a membrane of the piezoelectric plate using an etchant introduced through holes in the piezoelectric plate.

Provided is a composite substrate for surface acoustic wave device which does not cause peeling of an entire surface of a piezoelectric single crystal film even when heating the film to 400° C. or higher in a step after bonding. The composite substrate is formed by providing a piezoelectric single crystal substrate and a support substrate, forming a film made of an inorganic material on at least one of the piezoelectric single crystal substrate and the support substrate, and joining the piezoelectric single crystal substrate with the support substrate so as to sandwich the film made of the inorganic material.

A bulk acoustic wave resonator is provided. The bulk acoustic wave resonator includes a board; a resonant portion including a first electrode, a piezoelectric layer, and a second electrode, and disposed on the board, and a temperature compensation layer disposed on the resonant portion, wherein the temperature compensation layer includes a temperature compensation portion formed of a dielectric and a loss compensation portion formed of a material different from a material of the temperature compensation portion, and wherein each of the temperature compensation portion and the loss compensation portion includes a plurality of linear patterns, and the linear patterns of the temperature compensation portion and the linear patterns of the loss compensation portion are alternately disposed.

A resonator device comprising a piezoelectric material and at least one electrode, the device also provided with a material with a positive coefficient of stiffness, wherein the material is disposed in the device as an electrode or as a separate layer adjacent the piezoelectric material formed as one or more layers in the device. The material that performs the temperature compensating function is selected from the group consisting of ferromagnetic metal alloys, shape-memory metal alloys, and polymers, wherein the selected material has a temperature coefficient that varies with the relative amounts of the individual constituents of the compositions and wherein the composition is selected to provide the material with the positive coefficient of stiffness.

A vibration element includes: a quartz crystal substrate having a first vibration part and a second vibration part; a pair of first excitation electrodes formed at two main surfaces of the quartz crystal substrate, at the first vibration part; and a pair of second excitation electrodes formed in such a way as to sandwich the second vibration part in a direction of thickness of the quartz crystal substrate, at the second vibration part. At least one second excitation electrode of the pair of second excitation electrodes is formed at an inclined surface inclined to at least one of the two main surfaces.

A crystal resonator includes a crystal element and excitation electrodes. The crystal element has a pair of principal surfaces parallel to an X′-axis and a Z′-axis. The X′-axis is an axis of rotating an X-axis as a crystallographic axis of a crystal in a range of 15 degrees to 25 degrees around a Z-axis as a crystallographic axis of the crystal. The Z′-axis is an axis of rotating the Z-axis in a range of 33 degrees to 35 degrees around the X′-axis. The excitation electrodes are formed on the respective principal surfaces of the crystal element. Elliptical mesa portions or elliptical inverted mesa portions are formed on the respective principal surfaces. The mesa portions project from outer peripheries of the principal surfaces. The inverted mesa portions are depressed from the outer peripheries of the principal surfaces.

A piezoelectric film that includes crystalline AlN; at least one first element partially replacing Al in the crystalline AlN; and a second element doping the crystalline AlN and which has an ionic radius smaller than that of the first element and larger than that of Al.