A semiconductor device includes a transistor implemented over an oxide layer, one or more electrical connections to the transistor, one or more dielectric layers formed over at least a portion of the electrical connections, an electrical element disposed over the one or more dielectric layers, the electrical element being in electrical communication with the transistor via the one or more electrical connections, a patterned form of sacrificial material covering at least a portion of the electrical element, and an interface layer covering at least a portion of the one or more dielectric layers and the sacrificial material.

A method for fabricating a semiconductor device involves providing a transistor device formed over an oxide layer formed on a semiconductor substrate, removing at least part of the semiconductor substrate, applying an interface material below to at least a portion of the oxide layer, removing a portion of the interface material to form a trench, and at least partially covering the interface material and the trench with a substrate layer to form a cavity

A method for fabricating a radio-frequency device involves providing a semiconductor wafer including a transistor device, applying a form of sacrificial material on the semiconductor wafer, applying an interface material over the form of sacrificial material, and removing at least a portion of the form of sacrificial material to form a cavity at least partially covered by the interface material.

An amplifying radiofrequency device includes a piezoelectric film and a semiconductor amplifier layer. The piezoelectric film is conformed as an acoustic waveguide. The piezoelectric film has a principal acoustic propagation direction parallel to the principal conduction direction of the amplifier layer. Interdigitated transducers are positioned on the piezoelectric film to respectively launch an acoustic wave in response to an input RF signal, and transduce the acoustic wave back to an output RF signal. There is a distance of less than the acoustic wavelength between the semiconductor amplifier layer and the piezoelectric film. The piezoelectric film has a thickness of less than the acoustic wavelength. According to a method for making such a device, a stack of III-V layers is epitaxially grown on a III-V substrate, wherein the stack comprises a first etch stop layer, a second etch stop layer, an amplifier layer, and a contact layer. The stack is bonded to a lithium niobate film. The III-V substrate is removed by etching down to the first etch stop layer. Deposition windows are opened by etching from the first etch stop layer down to the contact layer. Metal contact electrodes are deposited in the deposition windows.

A method for fabricating a semiconductor die involves providing a semiconductor substrate, forming a plurality of active devices and a plurality of passive devices over the semiconductor substrate, forming one or more electrical connections to the plurality of active devices and the plurality of passive devices, forming one or more dielectric layers over at least a portion of the electrical connections, applying an interface material over at least a portion of the one or more dielectric layers, removing portions of the interface material to form a plurality of trenches, and covering at least a portion of the interface material and the plurality of trenches with a substrate layer to form a plurality of radio-frequency isolation cavities.

An acoustic wave device includes a functional electrode provided on a first main surface of an element substrate, extended wiring lines that are electrically connected to the functional electrode and that are adjacent to each other on a second main surface facing away from the first main surface, external terminals that are connected to the extended wiring lines, respectively, and that are provided on the second main surface, a first resin portion that seals the acoustic wave device, and a second resin portion that is provided at a position which is between the element substrate and the first resin portion and which is on the second main surface.

Fabrication of radio-frequency (RF) devices involves providing a field-effect transistor (FET), forming one or more electrical connections to the FET, forming one or more dielectric layers over at least a portion of the electrical connections, and disposing an electrical element over the one or more dielectric layers, the electrical element being in electrical communication with the FET via the one or more electrical connections. RF device fabrication further involves covering at least a portion of the electrical element with a sacrificial material, applying an interface material over the one or more dielectric layers, the interface material at least partially covering the sacrificial material, and removing at least a portion of the sacrificial material to form a cavity at least partially covered by the interface layer.

A semiconductor device includes a transistor device implemented over an oxide layer, an interface layer applied below at least a portion of the oxide layer, the interface layer having a trench formed therein, and a substrate layer covering at least a portion of the interface layer and the trench to form a cavity.

A superconducting device that mixes surface acoustic waves and techniques for fabricating the same are provided. A superconducting device can comprise a first surface acoustic wave resonator comprising a first low-loss piezo-electric dielectric substrate. The superconducting device can also comprise a second surface acoustic wave resonator comprising a second low-loss piezo-electric dielectric substrate. Further, the superconducting device can comprise a Josephson ring modulator coupled to the first surface acoustic wave resonator and the second surface acoustic wave resonator. The Josephson ring modulator is a dispersive nonlinear three-wave mixing element.

An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity V.sub.si=(V.sub.1).sup.1/2 of propagation through silicon or higher than the acoustic velocity V.sub.si, where V.sub.si is specified by V.sub.1 among solutions V.sub.1, V.sub.2, and V.sub.3 with respect to x derived from Ax.sup.3+Bx.sup.2+Cx+D=0.