Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a substrate having a front surface and an intervening oxide layer on the front surface and having a cavity. A thickness of the intervening oxide layer defines a depth of the cavity, and the substrate has vertical etch-stop material for etching the intervening oxide layer. Lateral fences formed in the intervening oxide layer define a perimeter of the cavity. The lateral fences has a lateral etch-stop material for etching the intervening oxide layer. A single-crystal piezoelectric plate has a back surface attached to the front surface of the intervening oxide layer except for a portion of the piezoelectric plate forming a diaphragm that spans the cavity. An interdigital transducer is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm.

Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a substrate having a front surface and a cavity. A depth of the cavity is defined by a buried oxide layer comprising etch-stop material and a perimeter of the cavity is defined by lateral fences 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.

A bulk acoustic wave filter includes: a first bulk acoustic wave resonator including, in an order from bottom to top, a first cavity, a first bottom electrode, a first segment of a piezoelectric layer, and a first top electrode; a second bulk acoustic wave resonator disposed adjacent to the first bulk acoustic wave resonator, and including, in the order from bottom to top, a second cavity, a second bottom electrode, a second segment of the piezoelectric layer, and a second top electrode; a boundary structure surrounding the first cavity and the second cavity, the boundary structure including a boundary portion extending between and separating the first cavity and the second cavity, and the boundary portion being disconnected at a disconnection region; and a first release hole formed in the piezoelectric layer, and overlapping the disconnection region.

An acoustic resonator that has a first electrode with a first planar portion. A second electrode having a second planar portion is disposed parallel to the first planar portion. This second electrode has a bifurcated end that defines a gap. A piezoelectric layer is disposed between and contacts both the first planar portion and the second planar portion. Also contacting the piezoelectric layer is the bifurcated end of the second electrode. The gap is formed in the periphery of each resonator within a filter. It is formed in the top electrode, that is typically formed of molybdenum, but could be formed from other metals as well. Unlike a gap between a top electrode and piezoelectric material, the gap recited herein is entirely within the second electrode. This structure is compatible with an inner passivation layer that enables a single crystal piezoelectric layer and a larger bottom electrode.

A bulk acoustic resonator includes: a substrate; a protective layer; and a resonant portion including a piezoelectric layer, a first electrode disposed between the piezoelectric layer and the substrate, and a second electrode disposed between the piezoelectric layer and the protective layer. The protective layer covers a central portion of the resonant portion and a reflective portion surrounding the central portion and formed in a region in which an upper surface of the second electrode rises relative to the central portion. An upper surface of a portion of the protective layer covering the reflective portion is more gently inclined than the upper surface of a portion of the second electrode in the reflective portion.

Acoustic resonators, filters, and methods. An acoustic resonator includes a substrate, piezoelectric plate, and a diaphragm comprising a portion of the piezoelectric plate spanning a cavity in a substrate. An interdigital transducer (IDT) on a front surface of the piezoelectric plate includes first and second sets of interleaved interdigital transducer (IDT) fingers extending from first and second busbars respectively. The interleaved IDT fingers are on the diaphragm. Overlapping portions of the interleaved IDT fingers define an aperture of the acoustic resonator. A first dielectric strip overlaps the IDT fingers in a first margin of the aperture and extends into a first gap between the first margin and the first busbar. A second dielectric strip overlaps the IDT fingers in a second margin of the aperture and extends into a second gap between the second margin and the second busbar.

A method of forming an Al.sub.1-xSc.sub.xN film can include heating a substrate, in a reactor chamber, to a temperature range, providing a precursor comprising Sc to the reactor chamber, providing a dopant comprising Mg, C, and/or Fe to the reactor chamber, and forming an epitaxial Al.sub.1-xSc.sub.xN film on the substrate in the temperature range, the epitaxial Al.sub.1-xSc.sub.xN film including the dopant in a concentration in a range between about 1×10.sup.17/cm.sup.3 and about 2×10.sup.20/cm.sup.3 on the substrate.

A bulk acoustic wave (BAW) resonator includes: a substrate; a piezoelectric layer disposed above the substrate; a first electrode disposed below the piezoelectric layer and including a first portion and a second portion spaced apart from each other; a second electrode disposed above the piezoelectric layer; a first dielectric layer, a second dielectric layer, and a third dielectric layer sequentially disposed between the substrate and the piezoelectric layer in an order from the piezoelectric layer to the substrate; a cavity disposed below the first portion of the first electrode; a metal bonding layer disposed between the third dielectric layer and the substrate; and a ground pad metal layer disposed on the piezoelectric layer and electrically connected to the metal bonding layer.

An acoustic wave device includes a support including a cavity, a piezoelectric layer on or above the support and made of one of lithium niobate or lithium tantalate, an interdigital transducer electrode embedded in the piezoelectric layer and including surfaces opposed to each other in a thickness direction, one of the surfaces being in contact with the piezoelectric layer, and a dielectric film on the piezoelectric layer and covering the interdigital transducer electrode. The interdigital transducer electrode includes electrode fingers, at least one of which overlaps the cavity in plan view. Assuming a thickness of the piezoelectric layer is d and an electrode finger pitch of the interdigital transducer electrode is p, p/d≥ about 4.25.

A piezoelectric film laminated body includes a metal film, an amorphous film, and a scandium aluminum nitride film. The amorphous film has an insulation property and is disposed on the metal film. The scandium aluminum nitride film is disposed on the amorphous film and is in contact with a surface of the amorphous film.