The present disclosure relates to semiconductor structures and, more particularly, to bipolar transistors and methods of manufacture. The structure includes: a base region composed of a semiconductor on insulator material; an emitter region above the base region; and a collector region under the base region and within a cavity of a buried insulator layer.

An integrated circuit may be formed by forming a buried isolation layer in an isolation recess in a single-crystal silicon-based substrate. Exposed lateral surfaces of the substrate at the buried isolation layer are covered with a dielectric sidewall. A seed trench is formed through the buried isolation layer to expose the substrate. A single-crystal silicon-based seed layer is formed through the seed trench, extending above the top surface of the buried isolation layer. A silicon-based non-crystalline layer is formed contacting the seed layer. A cap layer is formed over the non-crystalline layer. A radiant-induced recrystallization process converts the non-crystalline layer to a single-crystal layer aligned with the seed layer. The cap layer is removed and the single-crystal layer is planarized, leaving an isolated semiconductor layer over the buried isolation layer.

A semiconductor device includes a trench extending through a semiconductor substrate and an epitaxial layer disposed over a first side of the semiconductor substrate. The epitaxial layer partially fills a portion of the trench. The semiconductor device further includes a back side metal layer disposed over a second side of the semiconductor substrate. The back side metal layer extends into the trench and fills the remaining portion of the trench. The epitaxial layer partially filling the trench contacts the back side metal layer filling the remaining portion within the trench.

An integrated circuit may be formed by forming a buried isolation layer in an isolation recess in a single-crystal silicon-based substrate. Exposed lateral surfaces of the substrate at the buried isolation layer are covered with a dielectric sidewall. A seed trench is formed through the buried isolation layer to expose the substrate. A single-crystal silicon-based seed layer is formed through the seed trench, extending above the top surface of the buried isolation layer. A silicon-based non-crystalline layer is formed contacting the seed layer. A cap layer is formed over the non-crystalline layer. A radiant-induced recrystallization process converts the non-crystalline layer to a single-crystal layer aligned with the seed layer. The cap layer is removed and the single-crystal layer is planarized, leaving an isolated semiconductor layer over the buried isolation layer.

A semiconductor single crystal structure may include a substrate; a defect trapping stack disposed on the substrate; and a semiconductor single crystal disposed on the defect trapping stack, and having a lattice mismatch with a crystal of the substrate, in which the defect trapping stack may include a first dielectric layer disposed on the substrate, and having at least one first opening, a second dielectric layer disposed on the first dielectric layer, and having at least one second opening, a third dielectric layer disposed on the second dielectric layer, and having at least one third opening, and a fourth dielectric layer disposed on the third dielectric layer, and having at least one fourth opening, and in which the semiconductor single crystal may extend to a region of the substrate defined in the at least one first opening through the at least one first to fourth opening.

Techniques are disclosed for gallium nitride (GaN) oxide isolation and formation of GaN transistor structures on a substrate. In some cases, the GaN transistor structures can be used for system-on-chip integration of high-voltage GaN front-end radio frequency (RF) switches on a bulk silicon substrate. The techniques can include, for example, forming multiple fins in a substrate, depositing the GaN layer on the fins, oxidizing at least a portion of each fin in a gap below the GaN layer, and forming one or more transistors on and/or from the GaN layer. In some cases, the GaN layer is a plurality of GaN islands, each island corresponding to a given fin. The techniques can be used to form various non-planar isolated GaN transistor architectures having a relatively small form factor, low on-state resistance, and low off-state leakage, in some cases.

Semiconductor structures are provided. A semiconductor structure includes a bottom substrate having a first region and a second region; an insulation layer formed on the bottom substrate in the first region; a top substrate on side surface of the trench and the insulation layer; a first fin portion formed over the insulation layer, and a gate structure crossing the first fin portion. The first fin portion is electrically isolated from the bottom substrate through the insulation layer to reduce the leakage current at the bottom of the first fin portion. The gate structure covers part of side and top surfaces of the first fin portion.

A method of fabricating a semiconductor device includes forming a buried insulation region within a substrate by processing the substrate using etching and deposition processes. A semiconductor layer is formed over the buried insulation region at a first side of the substrate. Device regions are formed in the semiconductor layer. The substrate is thinned from a second side of the substrate to expose the buried insulation region. The buried insulation region is selectively removed to expose a bottom surface of the substrate. A conductive region is formed under the bottom surface of the substrate.

In accordance with an embodiment of the present invention, a method of fabricating a semiconductor device includes forming openings partially filled with a sacrificial material, where the openings extend into a semiconductor substrate from a first side. A void region is formed in a central region of the openings. An epitaxial layer is formed over the first side of the semiconductor substrate and the openings, where the epitaxial layer covers the void region. From a second side of the semiconductor substrate opposite to the first side, the semiconductor substrate is thinned to expose the sacrificial material. The sacrificial material in the openings is removed and the epitaxial layer is exposed. A conductive material is deposited on the exposed surface of the epitaxial layer.

The invention relates to a method for manufacturing a transistor comprising the preparation of a stack of layers of the semiconductor on insulator type comprising at least one substrate on which an insulating layer and an initial semiconductor layer are successively disposed. The method includes the formation of at least one oxide pad extending from a top face of the insulating layer, the formation of an additional layer made from semiconductor material covering the oxide pad and intended to form a channel for the transistor, the formation of a gate stack above the oxide pad, and the formation of a source and drain on either side of the gate stack.