Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a substrate having a front surface and a cavity, a perimeter of the cavity defined by a lateral etch-stop comprising etch-stop material. A back surface of a single-crystal piezoelectric plate is attached to the front surface of the substrate except for a portion of the piezoelectric plate that forms a diaphragm that spans the cavity. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm.

Techniques for improving structures, acoustic wave resonators, layers, and devices are disclosed, including filters, oscillators and systems that may include such devices. An acoustic wave device of this disclosure may comprise a substrate and a piezoelectric resonant volume. The piezoelectric resonant volume of the acoustic wave device may have a main resonant frequency. The acoustic wave device may comprise a first distributed Bragg acoustic reflector. The first distributed Bragg acoustic reflector may comprise a first active piezoelectric layer. The main resonant frequency of the Bulk Acoustic Wave (BAW) resonator may be in a super high frequency (SHF) band. The main resonant frequency of the Bulk Acoustic Wave (BAW) resonator may be in an extremely high frequency (EHF) band.

A bulk acoustic resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; and a protective layer disposed to cover at least the metal pad.

An acoustic wave device includes a piezoelectric layer that is made of lithium niobate or lithium tantalate, and a plurality of pairs of electrodes opposed to each other in a direction intersecting with a thickness direction of the piezoelectric layer, in which a bulk wave in a thickness shear primary mode is used or d/p is about 0.5 or lower when a thickness of the piezoelectric layer is d and a distance between centers of mutually adjacent electrodes among the plurality of pairs of electrodes is p. The plurality of pairs of electrodes include at least one pair of first electrodes of a first acoustic wave resonator and at least one pair of second electrodes of a second acoustic wave resonator. A direction orthogonal to a longitudinal direction of the second electrodes in the second acoustic wave resonator is inclined at an angle that is greater than 0° and smaller than 360° with respect to a direction orthogonal to a longitudinal direction of the first electrodes in the first acoustic wave resonator.

An acoustic wave device includes a piezoelectric layer that is made of lithium niobate or lithium tantalate, and a plurality of pairs of electrodes opposed to each other in a direction intersecting with a thickness direction of the piezoelectric layer, in which a bulk wave in a thickness shear primary mode is used or d/p is about 0.5 or lower when a thickness of the piezoelectric layer is d and a distance between centers of mutually adjacent electrodes among the plurality of pairs of electrodes is p. The plurality of pairs of electrodes include at least one pair of first electrodes of a first acoustic wave resonator and at least one pair of second electrodes of a second acoustic wave resonator. A direction orthogonal to a longitudinal direction of the second electrodes in the second acoustic wave resonator is inclined at an angle that is greater than 0° and smaller than 360° with respect to a direction orthogonal to a longitudinal direction of the first electrodes in the first acoustic wave resonator.

A vibration member is provided that includes a base with front and rear ends opposite to each other, and vibration arms fixed to the front end, extending away therefrom, and including at least one first vibration arm and a pair of second vibration arms positioned on both sides of a first vibration arm group including the at least one first vibration arm in a direction intersecting a longitudinal direction. A holding arm is provided that has one end connected to the base and the other end connected to a frame. A plurality of vibration portions include a piezoelectric film, and a lower electrode and an upper electrode that sandwich the piezoelectric film. A connection wiring line that connects the respective upper electrodes of the pair of second vibration arms to each other is provided in a region of at least either of the base or the holding arm.

A vibration member is provided that includes a base with front and rear ends opposite to each other, and vibration arms fixed to the front end, extending away therefrom, and including at least one first vibration arm and a pair of second vibration arms positioned on both sides of a first vibration arm group including the at least one first vibration arm in a direction intersecting a longitudinal direction. A holding arm is provided that has one end connected to the base and the other end connected to a frame. A plurality of vibration portions include a piezoelectric film, and a lower electrode and an upper electrode that sandwich the piezoelectric film. A connection wiring line that connects the respective upper electrodes of the pair of second vibration arms to each other is provided in a region of at least either of the base or the holding arm.

A bulk acoustic resonator package is provided. The bulk acoustic resonator package includes a substrate; a cap; a resonance portion including a first electrode, a piezoelectric layer, and a second electrode, stacked in a first direction in which the substrate and the cap face each other, and disposed between the substrate and the cap; and a cap melting member disposed to surround the resonance portion, and disposed to be in contact with a portion of a surface of the cap facing the substrate, when viewed in the first direction, and including a material or a structure that is based on a melting of the portion of the surface of the cap.

A bulk acoustic resonator package is provided. The bulk acoustic resonator package includes a substrate; a cap; a resonance portion including a first electrode, a piezoelectric layer, and a second electrode, stacked in a first direction in which the substrate and the cap face each other, and disposed between the substrate and the cap; and a cap melting member disposed to surround the resonance portion, and disposed to be in contact with a portion of a surface of the cap facing the substrate, when viewed in the first direction, and including a material or a structure that is based on a melting of the portion of the surface of the cap.

An acoustic filter device includes first and second series resonators and at least one shunt resonator, each shunt resonator electrically coupled to the first series resonator or the second series resonator. Each of the first and second series resonators includes respective first and second sub-resonators electrically connected in series, The first sub-resonators of the first and second series resonators are acoustically coupled along a first shared acoustic track. The second sub-resonators of the first and second series resonators are acoustically coupled along a second shared acoustic track.