A method of manufacture and structure for an acoustic resonator device having a hybrid piezoelectric stack with a strained single crystal layer and a thermally-treated polycrystalline layer. The method can include forming a strained single crystal piezoelectric layer overlying the nucleation layer and having a strain condition and piezoelectric layer parameters, wherein the strain condition is modulated by nucleation growth parameters and piezoelectric layer parameters to improve one or more piezoelectric properties of the strained single crystal piezoelectric layer. Further, the method can include forming a polycrystalline piezoelectric layer overlying the strained single crystal piezoelectric layer, and performing a thermal treatment on the polycrystalline piezoelectric layer to form a recrystallized polycrystalline piezoelectric layer. The resulting device with this hybrid piezoelectric stack exhibits improved electromechanical coupling and wide bandwidth performance.

Aspects of this disclosure relate to bulk acoustic wave devices that have a raised frame structure, and filters that utilize the bulk acoustic wave devices. The raised frame structure can include a first raised frame layer that has a relatively low acoustic impedance. The raised frame structure can include a second raised frame layer that has a relatively high acoustic impedance. The first raised frame layer can extend inward further than the second raised frame layer. A width of the first raised frame layer that overlaps the first and second electrodes is between about 1.5 times to about 4 times larger than the combined thickness of the first electrode, the piezoelectric layer, and the second electrode.

Aspects of this disclosure relate to bulk acoustic wave devices that have a raised frame structure. The raised frame structure can include a first raised frame layer that has a relatively low acoustic impedance. The raised frame structure can include a second raised frame layer that has a relatively high acoustic impedance. The first raised frame layer can have a thickness that is between about 0.02 and about 0.4 times the combined thickness H of the bulk acoustic wave device. The first raised frame layer can have a thickness that is between about 0.01 and about 0.2 times the resonant wavelength λ of the bulk acoustic wave device.

In a method for forming a film bulk acoustic resonator (FBAR), a bulk acoustic wave (BAW) film stack (120) and a support structure (130) are successively formed on a first substrate (100). The support structure (130) includes a primary support wall (131), an isolation wall (132) internal to the primary support wall (131) and a secondary support pillar (133) internal to the isolation wall (132). After a second substrate (200) is bonded and the first substrate (100) is removed, the secondary support pillar (133) and the isolation wall (132) are removed through a release window (120a) in an area delimited by the isolation wall (132). The secondary support pillar (133) contributes to effective support provided during transfer of the films and any other process carried out above the support structure, the isolation wall (132) between the primary support wall (131) and the secondary support pillar (133) can protect the primary support wall (131) against erosion during a process for removing the secondary support pillar (133), providing for high reliability of a cavity (140) subsequently formed within an area delimited by the primary support wall (131).

An acoustic wave device including a support substrate, a piezoelectric layer provided over the support substrate, at least one pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the at least one pair of comb-shaped electrodes including electrode fingers, a temperature compensation film interposed between the support substrate and the piezoelectric layer, the temperature compensation film having a temperature coefficient of elastic constant opposite in sign to a temperature coefficient of elastic constant of the piezoelectric layer; and an insulating layer interposed between the support substrate and the temperature compensation film, a first surface of the insulating layer having first protruding portions and/or first recessed portions, a second surface of the insulating layer having second protruding portions and/or second recessed portions, the first surface being closer to the support substrate, the second surface being closer to the temperature compensation film.

Methods, systems, and devices are described for isolating a crystal oscillator assembly from shock and/or vibration inputs. A system may include one or more vibration isolators coupled between the crystal oscillator assembly and the base structure, and each of the vibration isolators may include a spring material layer and a damping material layer. The spring material layer may provide a spring force between the crystal oscillator assembly and the base structure. The damping material layer may be adhered to at least one side of the spring material layer, and may provide a damping force between the crystal oscillator assembly and the base structure. Some vibration isolators may further include a constraint layer adhered to the damping material layer, such that the damping material layer is coupled between the constraint layer and the spring material layer.

An acoustic wave device includes a support substrate having a thickness in a first direction, a piezoelectric layer on the support substrate, and an interdigital transducer electrode on the piezoelectric layer and including first and second electrode fingers extending in a second direction crossing the first direction. The second electrode fingers face the first electrode fingers in a third direction orthogonal or substantially orthogonal to the second direction. The support substrate and the piezoelectric layer include a hollow therebetween at a position at least partially overlapping the interdigital transducer electrode in the first direction. At least one through hole penetrates the piezoelectric layer at a position not overlapping the interdigital transducer electrode in the first direction, and the through hole communicates with the hollow. A reinforcing support extends inside the hollow in a region overlapping the hollow and not overlapping the first and second electrode fingers.

In an example, a system includes a BAW resonator. The system also includes a first heater configured to heat the BAW resonator, where the first heater is controlled by a first control loop. The system includes a circuit coupled to the BAW resonator. The system also includes a second heater configured to heat the circuit, where the second heater is controlled by a second control loop.

Aspects of this disclosure relate to a bulk acoustic wave device with a floating raised frame structure. The bulk acoustic wave device includes a first electrode, a second electrode, a piezoelectric layer positioned between the first electrode and the second electrode, and a floating raised frame structure positioned on a same side of the piezoelectric layer as the first electrode and spaced apart from the first electrode. The floating raised frame structure is at a floating potential. The bulk acoustic wave device can suppress a raised frame mode. Related methods, filters, multiplexers, radio frequency front ends, radio frequency modules, and wireless communication devices are disclosed.

Devices and processes for preparing devices are described for a bulk acoustic wave resonator. A stack includes a first electrode that is coupled to a first side of a piezoelectric layer and a second electrode that is coupled to a second side of the piezoelectric layer. The stack is configured to resonate in response to an electrical signal applied between the first electrode and the second electrode. A cavity frame is coupled to the first electrode and to the substrate. The cavity frame forms a perimeter around a cavity. Optionally, a heat dissipating frame is formed and coupled to the second electrode. The cavity frame and/or the heat dissipating frame improve the thermal stability of the bulk acoustic resonator.