A laterally excited bulk acoustic wave device is disclosed. The laterally excited bulk acoustic wave device can include a support substrate, a solid acoustic mirror on the support substrate, a piezoelectric layer on the solid acoustic mirror, and an interdigital transducer electrode on the piezoelectric layer. The interdigital transducer electrode is arranged to laterally excite a bulk acoustic wave.

A bulk acoustic wave filter includes series resonators connected to a series arm, and parallel resonators connected to a parallel arm connected to the series arm. Two or more of the series resonators are disposed in parallel on the series arm, and each includes a substrate, a lower electrode on the substrate, a piezoelectric layer on the lower electrode, and an upper electrode on the piezoelectric layer, wherein, when an active region in which the lower electrode, the piezoelectric layer, and the upper electrode overlap each other is viewed from above, a centroid of the active region and a center of a rectangle defining an aspect ratio of the active region match each other, and when the active region is viewed from above, the active region has a shape of polygon symmetrical with respect to at least one axis passing through a center of the rectangle defining the aspect ratio.

A bulk acoustic wave filter includes series resonators connected to a series arm, and parallel resonators connected to a parallel arm connected to the series arm. Two or more of the series resonators are disposed in parallel on the series arm, and each includes a substrate, a lower electrode on the substrate, a piezoelectric layer on the lower electrode, and an upper electrode on the piezoelectric layer, wherein, when an active region in which the lower electrode, the piezoelectric layer, and the upper electrode overlap each other is viewed from above, a centroid of the active region and a center of a rectangle defining an aspect ratio of the active region match each other, and when the active region is viewed from above, the active region has a shape of polygon symmetrical with respect to at least one axis passing through a center of the rectangle defining the aspect ratio.

Aspects of the disclosure relate to wireless communication filtering. One aspect is an apparatus including a first acoustic resonator that is part of a first bandpass filter having a first passband and coupled to a circuitry connection port and a communication connection port, and a second acoustic resonator that is part of one of a second bandpass filter or a notch filter. The apparatus further includes a third acoustic resonator that is part of the first bandpass filter, and a fourth acoustic resonator that is part of the second bandpass filter or the notch filter.

Acoustic resonator devices are disclosed. An acoustic resonator device includes a plurality of cells electrically connected in parallel. Each cell includes an interdigital transducer (IDT) on a piezoelectric plate, the IDT having at least 15 and not more than 35 interleaved fingers.

A laterally excited bulk acoustic wave device is disclosed. The laterally excited bulk acoustic wave device can include a first solid acoustic mirror, a second solid acoustic mirror, a piezoelectric layer that is positioned between the first solid acoustic mirror and the second solid acoustic mirror, an interdigital transducer electrode on the piezoelectric layer, and a support substrate arranged to dissipate heat associated with the bulk acoustic wave. The interdigital transducer electrode is arranged to laterally excite a bulk acoustic wave. The first solid acoustic mirror and the second solid acoustic mirror are arranged to confine acoustic energy of the bulk acoustic wave. The first solid acoustic mirror is positioned on the support substrate.

A laterally excited bulk acoustic wave device is disclosed. The laterally excited bulk acoustic wave device can include a first solid acoustic mirror, a second solid acoustic mirror, a piezoelectric layer that is positioned between the first solid acoustic mirror and the second solid acoustic mirror, an interdigital transducer electrode on the piezoelectric layer, and a support substrate arranged to dissipate heat associated with the bulk acoustic wave. The interdigital transducer electrode is arranged to laterally excite a bulk acoustic wave. The first solid acoustic mirror and the second solid acoustic mirror are arranged to confine acoustic energy of the bulk acoustic wave. The first solid acoustic mirror is positioned on the support substrate.

A method of making a SiC resonator includes forming a layer of an oxide material on a relatively thick wafer of SiC; bonding the layer of oxide material on the relatively thick wafer of SiC to a handle wafer having at least an oxide exterior surface, the resulting bond being substantially free of voids; planarizing the relatively thick wafer of SiC to a desired thickness; forming top and bottom electrodes on the wafer of SiC wafer to define a SiC wafer resonator portion; and forming a trench around the top and bottom electrodes, the tench completely penetrating the planarized wafer of SiC around a majority of a distance surrounding said top and bottom electrodes, except for one or more tether regions of the planarized wafer of SiC which remain physically coupled a remaining portion the SiC wafer resonator portion which defines a frame formed of the planarized wafer of SiC surrounding the SiC wafer resonator portion.

A method of making a SiC resonator includes forming a layer of an oxide material on a relatively thick wafer of SiC; bonding the layer of oxide material on the relatively thick wafer of SiC to a handle wafer having at least an oxide exterior surface, the resulting bond being substantially free of voids; planarizing the relatively thick wafer of SiC to a desired thickness; forming top and bottom electrodes on the wafer of SiC wafer to define a SiC wafer resonator portion; and forming a trench around the top and bottom electrodes, the tench completely penetrating the planarized wafer of SiC around a majority of a distance surrounding said top and bottom electrodes, except for one or more tether regions of the planarized wafer of SiC which remain physically coupled a remaining portion the SiC wafer resonator portion which defines a frame formed of the planarized wafer of SiC surrounding the SiC wafer resonator portion.

An acoustic resonator has a substrate having a surface and a single-crystal piezoelectric plate, with a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on a surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The ends of IDT interleaved fingers or inner surfaces of the opposing busbars have a curved shape. In some cases, gaps between ends of the interleaved fingers and opposing busbars have one of circular gap shapes or parabolic gap shapes. The cavity may be formed in an intermediate layer of the substrate.