A method and structure for a transfer process for an acoustic resonator device. In an example, a bulk acoustic wave resonator (BAWR) with an air reflection cavity is formed. A piezoelectric thin film is grown on a crystalline substrate. Patterned electrodes are deposited on the surface of the piezoelectric film. An etched sacrificial layer is deposited over the electrodes and a planarized support layer is deposited over the sacrificial layer. The device can include a dielectric protection layer (DPL) that protects the piezoelectric layer from etching processes that can produce rough surfaces and reduces parasitic capacitance around the perimeter of the resonator when the DPL's dielectric constant is lower than that of the piezoelectric layer. The DPL can be configured between the top electrode and the piezoelectric layer, between the bottom electrode and the piezoelectric layer, or both.

A method and structure for a transfer process for an acoustic resonator device. In an example, a bulk acoustic wave resonator (BAWR) with an air reflection cavity is formed. A piezoelectric thin film is grown on a crystalline substrate. One or more patterned electrodes are deposited on the surface of the piezoelectric film. An etched sacrificial layer is deposited over the one or more electrodes and a planarized support layer is deposited over the sacrificial layer. The support layer is etched to form one or more cavities overlying the electrodes to expose the sacrificial layer. The sacrificial layer is etched to release the cavities around the electrodes. Then, a cap layer is fusion bonded to the support layer to enclose the electrodes in the support layer cavities.

A method and structure for a transfer process for an acoustic resonator device. In an example, a bulk acoustic wave resonator (BAWR) with an air reflection cavity is formed. A piezoelectric thin film is grown on a crystalline substrate. A first patterned electrode is deposited on the surface of the piezoelectric film. An etched sacrificial layer is deposited over the first electrode and a planarized support layer is deposited over the sacrificial layer, which is then bonded to a substrate wafer. The crystalline substrate is removed and a second patterned electrode is deposited over a second surface of the film. The sacrificial layer is etched to release the air reflection cavity. Also, a cavity can instead be etched into the support layer prior to bonding with the substrate wafer. Alternatively, a reflector structure can be deposited on the first electrode, replacing the cavity.

A resonator element includes a substrate having a first region performing thickness shear vibration, a second region located in a periphery of the first region and having a smaller thickness than the first region, a fixed end, and a free end opposite to the fixed end in the first region in a plan view. Excitation electrodes are disposed on a front and a rear of the first region and have regions overlapping each other in the plan view. A center of the first region and a center of the regions overlapping each other are located between a center of the substrate and the free end in the plan view. When Cs is a distance between the center of the regions overlapping each other and the center of the substrate in the plan view, a relation of 105 μm<Cs<130 μm is satisfied.

A vibration element includes a crystal blank, a pair of excitation electrodes, and pair of extraction electrodes. The crystal blank is an AT cut crystal blank including a mesa part and an outer circumferential part which is thinner than the mesa part and surrounds the mesa part. The pair of excitation electrodes is provided on the two major surfaces of the mesa part. The pair of extraction electrodes include pad parts which are provided at the end parts of the crystal blank in the longitudinal direction on one major surface of the outer circumferential part and are connected to the pair of excitation electrodes. The length in the longitudinal direction of the crystal blank is less than 1000 μm. When the resonance frequency is F (MHz) and t=1670/F, the distance “y” (μm) between each of the pad parts and the mesa part satisfies 0.048F+1.18<y/t<0.097F+0.36.

A resonator element includes a vibrating portion that vibrates in a thickness shear vibration and includes a first main surface and a second main surface which are in a front and back relationship to each other, a first excitation electrode that is provided on the first main surface, and a second excitation electrode that is provided on the second main surface, and an energy trapping coefficient M satisfies a relationship of 33.6≦M≦65.1.

A crystal vibrator that includes a crystal substrate having a front surface and a rear surface, including a vibration portion in a region including a center of the crystal substrate, and a first peripheral portion that surrounds a periphery of the vibration portion and that has a smaller thickness than the vibration portion. Drive electrodes are formed on both surfaces of the vibration portion of the crystal substrate. In at least one of the front surface and the rear surface of the crystal substrate, a step is provided between the vibration portion and the first peripheral portion, and a first peripheral edge portion of the vibration portion and a second peripheral edge portion of the first peripheral portion are in a curved surface shape.

A piezoelectric vibration piece has an inverted mesa-type structure, comprising a thinned portion serving as a vibration region at a central part of a piezoelectric plate; and a thickened portion formed all along or partly along perimeter of the thinned portion to reinforce the thinned portion. In the piezoelectric vibration piece, contact metals including a large number of discrete metallic thin films are provided on the whole surfaces of the piezoelectric plate. A piezoelectric vibration device comprises the piezoelectric vibration piece which is housed in a package, wherein extraction electrodes of the piezoelectric vibration piece are connected to internal terminals of the package through a conductive adhesive. These structural and technical advantages prevent undesirable flowage of the conductive adhesive before thermal curing. As a result, the piezoelectric vibration piece and the piezoelectric vibration device comprising the same successfully attain excellent vibration characteristics.

The crystal element includes: a mesa-shaped crystal piece in a substantially rectangular shape in a plan view including an oscillation section having a first protruded section and a second protruded section; excitation electrodes provided on both main surfaces of the oscillation section; leading sections provided side by side along a prescribed side of the crystal piece; and a wiring section connecting between the excitation electrodes and the leading sections. The first protruded section and the second protruded section include sloping side faces. The side face of the first protruded section located on the +X-side overlaps with the side face of the second protruded section located on the +X side, and the side face of the first protruded section located on the −X-side overlaps with the side face of the second protruded section located on the −X side.

An AT-cut crystal element includes a vibrator and a supporting portion. The vibrator has a planar shape with an approximately rectangular shape. The supporting portion is connected to one short side of the vibrator and has a thickness thicker than a thickness of the vibrator. The AT-cut crystal element has an oscillation frequency of approximately 76 Mhz. The vibrator has a distal end portion that is an end portion on a side opposite to the supporting portion. The distal end portion is formed to have a protrusion shape toward a distal end side thereof. The vibrator has both ends formed to have a protrusion shape toward an outside direction along the short side. The vibrator has a long side dimension L and a short side dimension W. A W/L is in a range of 0.74 to 0.79 or in a range of 0.81 to 0.93.