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 rectangular quartz crystal blank having long sides substantially parallel to a Z axis of the quartz crystal blank, and short sides substantially parallel to an X axis of the quartz crystal blank. The quartz crystal blank includes a center region, a second region and a third region that are adjacent to the center region along a long-side direction, and a fourth region and a fifth region that are adjacent to the first region along a short-side direction. A thickness of the second region and a thickness of the third region are smaller than a thickness of the first region, and/or a thickness of the fourth region and a thickness of the fifth region are smaller than a thickness of the first region, and 16.21W/T17.71, where W is a length of a short side and T is a thickness.

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.

A crystal blank includes a pair of tableland-shaped first mesa parts projecting from a flat plate and a pair of tableland-shaped second mesa parts projecting from the pair of first mesa parts. The flat plate's length in a long direction is less than 1000 m. The first mesa part is on an inner side of the flat plate's major surface. The second mesa part is on the first mesa part's inner side of an upper surface's outer edge at two ends of the long direction and has a width equivalent to the first mesa part's upper surface at two sides of a short direction. An excitation electrode reaches the second mesa part's outer edge of the upper surface, is located on the inner side of the first mesa part, and on the second mesa part's inner side of the upper surface's outer edge at two sides of the short direction.

A bulk acoustic wave resonator includes: a substrate; a first electrode disposed above the substrate; a piezoelectric layer disposed above at least a portion of the first electrode; and a second electrode disposed above at least a portion of the piezoelectric layer. A first gap is formed between the piezoelectric layer and one of the first and second electrodes. The first gap includes a first inner gap disposed in an active area of the bulk acoustic wave resonator, and having a first spacing distance between the piezoelectric layer and the one of the first and second electrodes, and a first outer gap disposed outwardly of the active area and having a second spacing distance, different than the first spacing distance, between the piezoelectric layer and the one of the first and second electrodes.

An AT-cut crystal resonator plate includes: a vibrating part having a rectangular shape in plan view that is disposed on a center of the AT-cut crystal resonator plate and that has excitation electrodes respectively formed on a first and a second main surfaces; a cut-out part having a rectangular shape in plan view that is formed along an outer periphery of the vibrating part; an external frame part having a rectangular shape in plan view that is formed along an outer periphery of the cut-out part; and a connecting part that connects the vibrating part to the external frame part and that extends, in a Z axis direction of the vibrating part, from one end part of a side of the vibrating part along an X axis direction. The connecting part includes wide parts whose widths gradually increase only toward the external frame part.

A rectangular quartz crystal blank having long sides substantially parallel to a Z axis of the quartz crystal blank, and short sides substantially parallel to an X axis of the quartz crystal blank. The quartz crystal blank includes a center region, a second region and a third region that are adjacent to the center region along a long-side direction, and a fourth region and a fifth region that are adjacent to the first region along a short-side direction. A thickness of the second region and a thickness of the third region are smaller than a thickness of the first region, and/or a thickness of the fourth region and a thickness of the fifth region are smaller than a thickness of the first region, and 25.90W/T27.17, where W is a length of a short side and T is a thickness.

Oscillators that use resonator elements formed from langasite or one of its isomorphs are described herein. The resonator elements include crystal orientations that are stress and/or temperature compensated. The resonators vibrate at an oscillating frequency in a thickness-shear mode of vibration. The oscillating frequency can be used to derive temperature, derive pressure, and/or for frequency control applications.

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.

The oscillating element includes a crystal blank, a pair of excitation electrodes, and a pair of pad portions. The crystal blank includes a pair of major surfaces, at least partially configured by crystal planes, and side surfaces which connect outer edges of the pair of major surfaces. Further, it includes a mesa portion and an outer peripheral portion which surrounds the mesa portion and has a thickness between the pair of major surfaces thinner than that of the mesa portion. The excitation electrodes are individually located on the pair of major surfaces. The pair of pad portions are located on one of the pairs of major surfaces and are electrically connected with the excitation electrodes. At least a portion of an edge part which is in contact with a crystal plane includes a projecting portion, which does not exceed the height of the mesa portion from the outer peripheral portion.