An apparatus includes a substrate, a thin film piezoelectric layer, a transducer, and a low resistivity layer. The thin film piezoelectric layer is over the substrate, the transducer includes a number of electrodes in contact with the thin film piezoelectric layer and configured to transduce an acoustic wave in the thin film piezoelectric layer. The low resistivity layer is between at least a portion of the substrate and the thin film piezoelectric layer. By providing the low resistivity layer between at least a portion of the substrate and the thin film piezoelectric layer, a spurious response of the apparatus may be significantly reduced, thereby improving the performance thereof.

The invention discloses a bulk acoustic wave resonator and a manufacturing method thereof, the bulk acoustic wave resonator comprising: an air gap arranged at the external of the effective piezoelectric region, the air gap being formed between the upper electrode and the piezoelectric layer and/or between the piezoelectric layer and the substrate, and covering the end part, proximal to the air gap, of the lower electrode or connecting to the end part of the lower electrode, wherein the air gap is provided with a first end proximal to the effective piezoelectric region, and at least a portion of the upper surface, starting from the first end, of the air gap is an arch-shaped upper surface. The bulk acoustic wave resonator of the present invention capable of increasing a quality factor (Q) and an effective electromechanical coupling coefficient (K.sup.2.sub.t,eff) and improving the electrostatic discharge (ESD) immunity.

An electronic device, such as a filter, includes a first substrate having a bottom surface and a top surface, a first side wall of a certain height being formed along a periphery of the bottom surface to surround an electronic circuit disposed on the bottom surface, an external electrode formed on the top surface, the external electrode being connected to the electronic circuit by a via communicating with the bottom surface and a second substrate. The second substrate has a second side wall of a certain height formed along a periphery of a top surface, the second side wall being aligned and bonded with the first side wall to internally form a cavity defined between the bottom surface of the first substrate, the top surface of the second substrate, the first side wall, and the second side wall.

A bulk acoustic wave resonator includes: support members disposed between air cavities; a resonant part including a first electrode, a piezoelectric layer, and a second electrode sequentially disposed above the air cavities and on the support members; and a wiring electrode connected either one or both of the first electrode and the second electrode, and disposed above one of the air cavities, wherein a width of an upper surface of the support members is greater than a width of a lower surface of the support members, and side surfaces of the support members connecting the upper surface and the lower surface to each other are inclined.

An acoustic resonator includes a membrane layer disposed on an insulating layer; a cavity formed by the insulating layer and the membrane layer; a resonating portion disposed on the cavity and having a first electrode, a piezoelectric layer, and a second electrode stacked thereon; a protective layer disposed on the resonating portion; and a hydrophobic layer formed on the protective layer.

A hybrid acoustic resonator. An interdigital electrode is provided in a first region of a surface of a piezoelectric film facing away from a substrate, and forms an interdigital transducer. At least two trenches are provided in a second region of the surface of the piezoelectric film facing away from the substrate. A bulk-acoustic-wave propagation portion is formed between adjacent trenches. A bulk-acoustic-wave electrode is provided on a side surface of the bulk-acoustic-wave propagation portion, and there is an air gap at a surface of the bulk-acoustic-wave electrode facing away from the bulk-acoustic-wave propagation portion. Thereby, the hybrid acoustic resonator includes both the surface acoustic resonator and the bulk acoustic resonator. An acoustic wave in the bulk-acoustic-wave propagation portion and an acoustic wave in the interdigital transducer are both transmitted along a transversal direction.

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.

A bulk-acoustic wave resonator includes a substrate, a cavity formed in the substrate, a first electrode, a piezoelectric layer, and a second electrode stacked in order on the substrate, a resonator defined by the first electrode, the piezoelectric layer, and the second electrode overlapping in a vertical direction in an upper portion of the cavity, an additional layer disposed on one surface of the first electrode arranged in a wiring region on an external side of the resonator, and a wiring electrode connected to the first electrode arranged in the wiring region. The first electrode forms a contact interfacial surface with the additional layer and the wiring electrode.

Bulk acoustic wave resonators of two or more different filters can be on a common die. The two filters can be included in a multiplexer, such as a duplexer, or implemented as standalone filters. With bulk acoustic wave resonators of two or more filters on the same die, the filters can be implemented in less physical space compared to implementing the same filters of different die. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.

An RF integrated circuit device can includes a substrate and a High Electron Mobility Transistor (HEMT) device on the substrate including a ScAlN layer configured to provide a buffer layer of the HEMT device to confine formation of a 2DEG channel region of the HEMT device. An RF piezoelectric resonator device can be on the substrate including the ScAlN layer sandwiched between a top electrode and a bottom electrode of the RF piezoelectric resonator device to provide a piezoelectric resonator for the RF piezoelectric resonator device.