A stacked die XBAR filter device includes a first die containing one or more XBARs on a first surface, a second die containing one or more XBARs on a second surface, and one or more conductive vias through either the first die or the second die, where the first die is connected to the second die with the first surface facing the second surface.

The disclosure provides a resonator and a filter. The resonator includes: a substrate; and a multilayer structure formed on the substrate. The multilayer structure successively includes a lower electrode layer, a piezoelectric layer and an upper electrode layer from bottom to top. A cavity is formed between the substrate and the multilayer structure, and the cavity includes a lower half cavity below an upper surface of the substrate and an upper half cavity beyond the upper surface of the substrate and protruding toward the multilayer structure. A resonator with novel structure and good performance is formed by providing the cavity with the lower half cavity below the upper surface of the substrate and the upper half cavity above the upper surface of the substrate.

A single-crystal bulk acoustic wave resonators with better performance and better manufacturability and a process for fabricating the same are described. A low-acoustic-loss layer of one or more single-crystal and/or poly-crystal piezoelectric materials is epitaxially grown and/or physically deposited on a surrogate substrate, followed with the formation of a bottom electrode and then a support structure on a first side of the piezoelectric layer. The surrogate substrate is subsequently removed to expose a second side of the piezoelectric layer that is opposite to the first side. A top electrode is then formed on the second side of the piezoelectric layer, followed by further processes to complete the BAW resonator and filter fabrication using standard wafer processing steps. In some embodiments, the support structure has a cavity or an acoustic mirror adjacent the first electrode layer to minimize leakage of acoustic wave energy.

An acoustic wave device includes a support substrate having a thickness in a first direction, a piezoelectric layer extending in the first direction of the support substrate, and an interdigital transducer electrode extending in the first direction of the piezoelectric layer and including first electrode fingers and second electrode fingers. The first electrode fingers extend in a second direction orthogonal to the first direction, and the second electrode fingers extend in the second direction and face corresponding ones of the first electrode fingers in a third direction orthogonal to the first and second directions. The support substrate has a recess on a side adjacent to the piezoelectric layer and at a position at least partially overlapping the interdigital transducer electrode in plan view in the first direction. A filling made of a material different from a material of the support substrate is included in a portion of the recess.

An acoustic wave device that includes a piezoelectric substrate that has a piezoelectric layer and a hollow portion, and first and second electrodes and. The piezoelectric layer has a first region that overlaps the first and second electrodes and the hollow portion in plan view, a second region that does not overlap the hollow portion and surrounds the first region in plan view, and a third region that overlaps the hollow portion and is located between the first region and the second region in plan view. A portion including the border between the first region and the third region of a cross-sectional shape in a lamination direction of the piezoelectric substrate includes a curved-surface shape.

An apparatus is disclosed for partially suspending a piezoelectric layer using a dielectric. In an example aspect, the apparatus includes a microacoustic filter with a substrate layer, a piezoelectric layer, an electrode structure that is in contact with the piezoelectric layer, and a dielectric. The electrode structure includes multiple fingers arranged across a plane having a first axis that is perpendicular to the multiple fingers and a second axis that is parallel to the multiple fingers. The dielectric is configured to separate the piezoelectric layer from the substrate layer and define a cavity between the piezoelectric layer and the substrate layer. The dielectric is also configured to support the piezoelectric layer across at least three points along the first axis.

A method and structure for single crystal acoustic electronic device. The device includes a substrate having an enhancement layer formed overlying its surface region, a support layer formed overlying the enhancement layer, and an air cavity formed through a portion of the support layer. Single crystal piezoelectric material is formed overlying the air cavity and a portion of the enhancement layer. Also, a first electrode material coupled to the backside surface region of the crystal piezoelectric material and spatially configured within the cavity. A second electrode material is formed overlying the topside of the piezoelectric material, and a dielectric layer formed overlying the second electrode material. Further, one or more shunt layers can be formed around the perimeter of a resonator region of the device to connect the piezoelectric material to the enhancement layer.

A method of forming a piezoelectric thin film can include depositing a material on a first surface of a Si substrate to provide a stress neutral template layer. A piezoelectric thin film including a Group III element and nitrogen can be sputtered onto the stress neutral template layer and a second surface of the Si substrate that is opposite the first surface can be processed to remove that Si substrate and the stress neutral template layer to provide a remaining portion of the piezoelectric thin film. A piezoelectric resonator can be formed on the remaining portion of the piezoelectric thin film.

An acoustic wave device assembly is disclosed. The acoustic wave device assembly can include a first acoustic wave device that includes a first substrate, a first piezoelectric layer, a first solid acoustic mirror that is disposed between the first substrate and the first piezoelectric layer, and a first interdigital transducer electrode that is in contact with the first piezoelectric layer. The acoustic wave device assembly can include a second acoustic wave device that includes a second substrate, a second piezoelectric layer, a second solid acoustic mirror that is disposed between the second substrate and the second piezoelectric layer, a second interdigital transducer electrode that is in contact with the second piezoelectric layer, and a third solid acoustic mirror over the second interdigital transducer electrode. The first acoustic wave device and the second acoustic wave device being stacked on one another. The acoustic wave device assembly can include a spacer assembly that is disposed over the first piezoelectric layer.

An acoustic wave device assembly is disclosed. The acoustic wave device assembly can include a first acoustic wave device that includes a first substrate, a first piezoelectric layer, a first solid acoustic mirror that is disposed between the first substrate and the first piezoelectric layer, and a first interdigital transducer electrode that is embedded in the piezoelectric layer. The acoustic wave device assembly can include a second acoustic wave device that includes a second substrate, a second piezoelectric layer, a second solid acoustic mirror that is disposed between the second substrate and the second piezoelectric layer, and a second interdigital transducer electrode that is in contact with the second piezoelectric layer. The second acoustic wave device is stacked over the first acoustic wave device. The first acoustic wave device and the second acoustic wave device are spaced by a spacer assembly such that a cavity is formed between the first acoustic wave device and the second acoustic wave device.