Certain aspects of the present disclosure provide a bulk acoustic wave (BAW) resonator having a substrate with a heatsink region and an electrical insulator region. An example electroacoustic device generally includes a piezoelectric layer, a first electrode structure, a second electrode structure, one or more reflector layers, and a substrate having a heatsink region and an electrical insulator region. The heatsink region is arranged under a first portion of the first electrode structure, the first portion of the first electrode structure overlapping the second electrode structure. The insulator region is arranged under a second portion of the first electrode structure, the second portion of the first electrode structure being adjacent to the first portion of the first electrode structure.

A resonance structure of bulk acoustic wave resonator comprises a bottom electrode, a dielectric layer and a top electrode, wherein the dielectric layer is formed on the bottom electrode; the top electrode is formed on the dielectric layer. A resonance area is defined by the overlapping area of the projection of the bottom electrode, the dielectric layer and the top electrode. The resonance area has a contour. The contour includes at least three curved edges and is formed by connecting the at least three curved edges. Each curved edge is concave to a geometric center of the contour.

An acoustic wave device includes a support substrate, a piezoelectric layer provided over the support substrate, comb-shaped electrodes disposed on the piezoelectric layer, each of the comb-shaped electrodes including electrode fingers exciting an acoustic wave, a temperature compensation film interposed between the support substrate and the piezoelectric layer and having a temperature coefficient of an elastic constant opposite in sign to that of the piezoelectric layer, a boundary layer interposed between the support substrate and the temperature compensation film, an acoustic velocity of a bulk wave propagating through the boundary layer being higher than an acoustic velocity of a bulk wave propagating through the temperature compensation film and being lower than an acoustic velocity of a bulk wave propagating through the support substrate, and an intermediate layer interposed between the support substrate and the boundary layer and having a Q factor less than a Q factor of the boundary layer.

Acoustic resonator devices, filter devices, and methods of fabrication are disclosed. A resonator device includes a single-crystal piezoelectric plate having a front surface and a back surface opposite the front surface, wherein the back surface is coupled to a surface of a substrate. A floating back-side conductor pattern is formed on a portion of the back surface. A front-side conductor pattern including two electrodes is formed on a portion of the front surface opposite the back-side conductor.

Acoustic wave filter devices are disclosed. A device includes a layer providing or on a topmost layer of an acoustic reflector. The intermediary layer has a first region and a second region. The first region has a first layer thickness and the second region has a second layer thickness different from the first layer thickness. The device includes a first multilayer stack on the first region and a second multilayer stack on the second region of the intermediary layer. Each of the first and the second stacks includes a piezoelectric layer on a counter electrode that is located on the respective region, an input and an output electrode. Application of a radio frequency voltage between the input electrode and the counter electrode layer of the first stack creates acoustic resonance modes in the piezoelectric layer between the input and output electrodes of the first and the second stack.

An acoustic wave device includes a piezoelectric substrate in which a reverse-velocity surface is convex and an IDT electrode on the piezoelectric substrate. When an acoustic wave propagation direction is a first direction and a direction perpendicular or substantially perpendicular to the first direction is a second direction, the portion of the IDT electrode where first and second electrode fingers overlap in the first direction is a crossing region. The crossing region includes a center region centrally located in the second direction and a first and second edge regions located on two sides of the center region. Recesses 17 and 18 are respectively provided in portions of the piezoelectric substrate located in the first and second edge regions between the portions where the first and second electrode fingers are provided.

An acoustic resonator device includes a conductor pattern formed on a surface of a piezoelectric plate. The conductor pattern includes a first busbar, a second busbar, and n interleaved parallel fingers of an interdigital transducer (IDT), where n is a positive integer. The fingers extend alternately from the first and second busbars. A first finger and an n′th finger are at opposing ends of the IDT. The conductor pattern also includes a first reflector element proximate and parallel to the first finger and a second reflector element proximate and parallel to the n′th finger. A distance pr between the first reflector element and the first finger and between the second reflector element and the n′th finger is not equal to a pitch p of the IDT.

Bulk acoustic wave resonators are presented. Such resonators typically operate based on a dynamic nonuniform effective piezoelectricity in composite multilayer ferroelectrics with large electrostriction coefficients, like barium strontium titanate (BST). Harmonic resonance modes of a multilayer bulk acoustic wave resonator can be selectively excited with an electromechanical coupling coefficient equal to the fundament mode, which is contrary to the trend K2∝1/n2 exhibited by conventional piezoelectric bulk acoustic resonators. Such a resonator allows for the design of a new class of band-switching filters.

An acoustic resonator device includes a conductor pattern formed on a surface of a piezoelectric plate. The conductor pattern includes a first busbar, a second busbar, and n interleaved parallel fingers of an interdigital transducer (IDT), where n is a positive integer. The fingers extend alternately from the first and second busbars. A first finger and an n'th finger are at opposing ends of the IDT. The conductor pattern also includes a first reflector element proximate and parallel to the first finger and a second reflector element proximate and parallel to the n'th finger. A center-to-center distance pr between the first reflector element and the first finger and between the second reflector element and the n'th finger is greater than or equal to 1.2 times a pitch p of the IDT and less than or equal to 1.5 times the pitch p.

Certain aspects of the present disclosure provide a bulk acoustic wave (BAW) resonator having a substrate with a heatsink region and an electrical insulator region. An example electroacoustic device generally includes a piezoelectric layer, a first electrode structure, a second electrode structure, one or more reflector layers, and a substrate having a heatsink region and an electrical insulator region. The heatsink region is arranged under a first portion of the first electrode structure, the first portion of the first electrode structure overlapping the second electrode structure. The insulator region is arranged under a second portion of the first electrode structure, the second portion of the first electrode structure being adjacent to the first portion of the first electrode structure.