There are disclosed acoustic resonators, filter devices, and methods of fabricating acoustic resonators and filter devices. An acoustic resonator includes a piezoelectric plate having front and back surfaces, the back surface attached to a surface of a substrate except for portions of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern on the front surface includes an interdigital transducer (IDT) with interleaved fingers of the IDT disposed on the diaphragm. A plurality of holes is in the diaphragm, wherein each of the plurality of holes is configured to scatter spurious modes in the diaphragm.

A microelectromechanical resonator device is provided having two-dimensional resonant rods. The resonator device has a piezoelectric layer formed with a plurality of alternating rods and trenches. A bottom electrode is in contact with a bottom surface of the piezoelectric layer. A top electrode metal grating of conductive strips is aligned in contact with corresponding rods of the piezoelectric layer.

A piezoelectric device includes a container and an AT-cut crystal element. The AT-cut crystal element has at least one side surface intersecting with a Z-axis of the crystallographic axis of the crystal constituted of three surfaces. The first surface is a surface equivalent to a surface formed by rotating the principal surface by 43.5 with an X-axis of the crystal as a rotation axis. The second surface is a surface equivalent to a surface formed by rotating the principal surface by 575 with the X-axis. The third surface is a surface equivalent to a surface formed by rotating the principal surface by 425 with the X-axis. When two corner portions on a side of a second side opposed to the first side of the AT-cut crystal element are viewed in plan view, each of the two corner portions have an approximately right angle.

A bulk acoustic wave resonator includes: support members disposed between air cavities; a resonant part including a first electrode, a piezoelectric layer, and a second electrode sequentially disposed above the air cavities and on the support members; and a wiring electrode connected either one or both of the first electrode and the second electrode, and disposed above one of the air cavities, wherein a width of an upper surface of the support members is greater than a width of a lower surface of the support members, and side surfaces of the support members connecting the upper surface and the lower surface to each other are inclined.

A micro-electromechanical system (MEMS) device includes a support structure comprising a polycrystalline ceramic core, a first adhesion layer coupled to the polycrystalline ceramic core, a conductive layer coupled to the first adhesion layer, a second adhesion layer coupled to the conductive layer, and a barrier layer coupled to the second adhesion layer. The support structure defines a cavity. The MEMS device also includes a III-V membrane coupled to a portion of the support structure. A portion of the III-V membrane is suspended over the cavity defined by the support structure and defines a MEMS structure.

An RF filter comprising a resonator element and a polymer composition is provided. The polymer composition contains an aromatic polymer and has a melting temperature of about 240 C. or more. The polymer composition exhibits a dielectric constant of about 5 or less and dissipation factor of about 0.05 or less at a frequency of 10 GHz.

A method of manufacturing a bulk acoustic wave resonator includes: forming a sacrificial layer on a substrate protection layer; forming a membrane layer on the substrate protection layer to cover the sacrificial layer; and forming a cavity by removing the sacrificial layer using a gas mixture comprising a halide-based gas and an oxygen-containing gas, wherein a mixture ratio of the halide-based gas to the oxygen-containing gas in the gas mixture is in a range from 1.5 to 2.4.

A resonator element includes a first electrode that is installed on a resonance portion of one of main surfaces positioned on the front and rear surfaces of a substrate, and a second electrode that is installed on the resonance portion of the other of the main surfaces, an outer shape of the substrate includes a first side surface and a second side surface, are arranged in a second direction intersecting the first direction, the first side surface and the second side surface respectively include an inclined surface, the first electrode includes a first lead electrode installed on the inclined surface of the first side surface, a second electrode includes the second lead electrode installed on the inclined surface of the second side surface, and an angle formed between the inclined surface and the main surface is equal to or greater than 52 and equal to or less than 62.

A laminated Sc.sub.xAl.sub.1-xN BAW resonator with complementary-switchable operation in thickness extensional modes (TE.sub.l and TE.sub.N). The resonator comprises ferroelectric Sc.sub.xAl.sub.1-xN layers alternatively stacked with metal electrodes, enabling independent polarization switching of each piezoelectric layer. Opting for unanimous or alternative poling of the Sc.sub.xAl.sub.1-xN layers, the resonator can be switched to operate in two complementary states with either TE.sub.l or TE.sub.N active resonance modes of similarly large k.sub.t.sup.2.

An acoustic wave device includes: a first substrate having a first surface and a side surface; an acoustic wave resonator located on the first surface of the first substrate; and a first insulator film that covers the acoustic wave resonator and is in contact with at least a part, which is located closer to the first surface, of the side surface of the first substrate.