Acoustic resonator devices, filters, and methods are disclosed. An acoustic resonator includes a substrate and a piezoelectric plate having front and back surfaces, the back surface attached to a surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. At least one finger of the IDT is disposed in a groove in the diaphragm. A depth of the groove is less than a thickness of the at least one finger of the IDT.

An acoustic wave device includes a support substrate, an inorganic film over the support substrate, a piezoelectric layer over the inorganic film, and an electrode over the piezoelectric layer. A portion of the support substrate includes a hollow that overlaps at least a portion of the electrode in a thickness direction of the support substrate. An inner wall of the inorganic film is located farther from the hollow than a location on an inner wall of the support substrate, the location being closest to the piezoelectric layer, the inner wall of the support substrate defining the hollow.

An acoustic wave device includes a support substrate, an inorganic film over the support substrate, a piezoelectric layer over the inorganic film, and an electrode over the piezoelectric layer. A portion of the support substrate includes a hollow that overlaps at least a portion of the electrode in a thickness direction of the support substrate. An inner wall of the inorganic film is located farther from the hollow than a location on an inner wall of the support substrate, the location being closest to the piezoelectric layer, the inner wall of the support substrate defining the hollow.

The present disclosure provides a single crystal film bulk acoustic resonator, a manufacturing method for a single crystal film bulk acoustic resonator, and a filter, and relates to the technical field of filters. The method includes: sequentially forming a buffer layer, a piezoelectric layer, and a first electrode that are stacked on a temporary base substrate; forming a first bonding layer on the first electrode; providing a substrate; etching the substrate to form a plurality of first bumps on a surface of the substrate; forming a second bonding layer covering top surfaces of the plurality of first bumps on the surface of the substrate; and bonding the second bonding layer located at the top surfaces of the plurality of first bumps to the first bonding layer. During bonding, the area of the top surfaces of the first bumps can be controlled by etched grooves, so the area of the second bonding layer located at the top surfaces of the first bumps can be controlled, thereby realizing the control of a bonding area. By controlling the bonding area, the balance between the bonding requirement and the bonding reliability is realized.

The present disclosure provides a single crystal film bulk acoustic resonator, a manufacturing method for a single crystal film bulk acoustic resonator, and a filter, and relates to the technical field of filters. The method includes: sequentially forming a buffer layer, a piezoelectric layer, and a first electrode that are stacked on a temporary base substrate; forming a first bonding layer on the first electrode; providing a substrate; etching the substrate to form a plurality of first bumps on a surface of the substrate; forming a second bonding layer covering top surfaces of the plurality of first bumps on the surface of the substrate; and bonding the second bonding layer located at the top surfaces of the plurality of first bumps to the first bonding layer. During bonding, the area of the top surfaces of the first bumps can be controlled by etched grooves, so the area of the second bonding layer located at the top surfaces of the first bumps can be controlled, thereby realizing the control of a bonding area. By controlling the bonding area, the balance between the bonding requirement and the bonding reliability is realized.

The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator with tunable electromechanical coupling. The disclosed BAW resonator includes a bottom electrode, a top electrode, and a multilayer transduction structure sandwiched therebetween. Herein, the multilayer transduction structure is composed of multiple transduction layers, and at least one of the transduction layers is formed of a ferroelectric material, whose polarization will vary with an electric field across the ferroelectric material. Upon adjusting direct current (DC) bias voltage across the bottom electrode and the top electrode, an overall polarization of the multilayer transduction structure and an overall electromechanical coupling coefficient of the multilayer transduction structure are capable of being changed. Once the change of the overall electromechanical coupling coefficient of the multilayer transduction structure is completed, the overall electromechanical coupling coefficient of the multilayer transduction structure will remain unchanged after removing the DC bias voltage.

The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator with tunable electromechanical coupling. The disclosed BAW resonator includes a bottom electrode, a top electrode, and a multilayer transduction structure sandwiched therebetween. Herein, the multilayer transduction structure is composed of multiple transduction layers, and at least one of the transduction layers is formed of a ferroelectric material, whose polarization will vary with an electric field across the ferroelectric material. Upon adjusting direct current (DC) bias voltage across the bottom electrode and the top electrode, an overall polarization of the multilayer transduction structure and an overall electromechanical coupling coefficient of the multilayer transduction structure are capable of being changed. Once the change of the overall electromechanical coupling coefficient of the multilayer transduction structure is completed, the overall electromechanical coupling coefficient of the multilayer transduction structure will remain unchanged after removing the DC bias voltage.

The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator, which includes a bottom electrode, a top electrode structure, and a ferroelectric layer sandwiched in between. Herein, the ferroelectric layer is formed of a ferroelectric material, which has a box-shape polarization-electric field (P-E) curve. The ferroelectric layer includes a ferroelectric border (BO) portion positioned at a periphery of the ferroelectric layer and a ferroelectric central portion surrounded by the ferroelectric BO portion. The ferroelectric BO portion has a first polarization and a first electromechanical coupling coefficient, and the ferroelectric central portion has a second polarization and a second electromechanical coupling coefficient. An absolute value of the first polarization is less than an absolute value of the second polarization, and the first electromechanical coupling coefficient is less than the second electromechanical coupling coefficient. The ferroelectric central portion is configured to provide a resonance of the BAW resonator.

The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator, which includes a bottom electrode, a top electrode structure, and a ferroelectric layer sandwiched in between. Herein, the ferroelectric layer is formed of a ferroelectric material, which has a box-shape polarization-electric field (P-E) curve. The ferroelectric layer includes a ferroelectric border (BO) portion positioned at a periphery of the ferroelectric layer and a ferroelectric central portion surrounded by the ferroelectric BO portion. The ferroelectric BO portion has a first polarization and a first electromechanical coupling coefficient, and the ferroelectric central portion has a second polarization and a second electromechanical coupling coefficient. An absolute value of the first polarization is less than an absolute value of the second polarization, and the first electromechanical coupling coefficient is less than the second electromechanical coupling coefficient. The ferroelectric central portion is configured to provide a resonance of the BAW resonator.

A resonator includes a silicon substrate, a bottom electrode stacked on a portion of the silicon substrate, a piezoelectric layer covering the bottom electrode and another portion of the silicon substrate, a top electrode stacked on the piezoelectric layer, and a Bragg reflecting ring. The Bragg reflecting ring is formed on a side of the piezoelectric layer connected to the top electrode and surrounds the top electrode. The Bragg reflecting ring includes a Bragg high-resistivity layer and a Bragg low-resistivity layer alternately arranged along the radial direction of the Bragg reflecting ring. An acoustic impedance of the Bragg high-resistivity layer is greater than an acoustic impedance of the Bragg low-resistivity layer. The Bragg reflecting ring forms reflection surfaces to reflect the laterally propagating clutter waves, thereby suppressing the parasitic mode in the working frequency band, improving the frequency response curve of the resonator and the overall performance of the resonator.