There is provided a nitride crystal substrate comprising group-III nitride crystal and containing n-type impurities, wherein an absorption coefficient α is approximately expressed by equation (1) in a wavelength range of at least 1 μm or more and 3.3 μm or less: α=n Kλ.sup.a (1) (wherein, λ(μm) is a wavelength, α(cm.sup.−1) is absorption coefficient of the nitride crystal substrate at 27° C., n (cm.sup.−3) is a free electron concentration in the nitride crystal substrate, and K and a are constants, satisfying 1.5×10.sup.−19≤K≤6.0×10.sup.−19, a=3).

A method for forming a semiconductor structure. Two isolation structures are formed in a semiconductor. A cavity is etched in the semiconductor between the two isolation structures in the semiconductor. Dopants are implanted into a bottom side of the cavity to form a doped region in the semiconductor below the cavity between the two isolation structures. A contact is formed in the cavity. The contact is on the doped region and in direct contact with the doped region.

The present disclosure provides a semiconductor device. The semiconductor device comprises a substrate, a plurality of isolation regions in the substrate and an active region surrounded by the isolation regions. A p-type doped region is interposed between two n-type doped regions in the substrate. A buried gate structure is formed in the substrate and disposed between the p-type doped region and the n-type doped region. The buried gate structure comprises a gate conductive material, a gate insulating layer disposed over the gate conductive material and a gate liner surrounding the gate conductive material and the gate insulating layer. A plurality of contact plugs are formed on the p-type doped region and the plurality of n-type doped regions.

Methods of fabricating a semiconductor device include providing a semiconductor substrate that includes a plurality of epitaxial layers, including a channel layer and a permanent cap over the channel layer, where the permanent cap defines an upper surface of the semiconductor substrate, and forming a sacrificial cap over the permanent cap in an active region of the device, where the sacrificial cap comprises a semiconductor material that includes aluminum. The method also includes forming one or more current carrying regions (e.g., source and drain regions) in the semiconductor substrate in the active region of the device by performing an ion implantation process to implant ions through the sacrificial cap, and into the semiconductor substrate, completely removing the sacrificial cap in the active region of the device, while refraining from removing the permanent cap, and forming one or more current carrying contacts over the one or more current carrying regions.

The present invention relates to: a method for manufacturing a GaN-based power device, the method comprising a step of irradiating particle beams onto a silicon substrate of a GaN-based power device, in which the silicon substrate is included; and a GaN-based power device manufactured by the method for manufacturing a GaN-based power device.

A method includes providing a semiconductor body, forming a thermosensitive element on or within the semiconductor body, forming a structured laser-reflective mask on the upper surface of the semiconductor body that covers the thermosensitive element and includes first and second openings, and performing a laser thermal annealing process that transmits laser energy through the first and second openings and into the semiconductor body, wherein the thermosensitive element comprises a critical temperature at which the thermosensitive element is irreparably damaged, wherein the laser thermal annealing process brings portions of the semiconductor body that are underneath the first and second openings to above the critical temperature, and wherein during the laser thermal annealing process the thermosensitive element remains below the critical temperature.

A method for manufacturing a semiconductor device, includes: forming an alignment mark in a non-element region of a gallium-based compound semiconductor layer; and, after the forming of the alignment mark, forming an element structure in an element region of the gallium-based compound semiconductor layer. The forming of the alignment mark further includes: ion-implanting a metal into a part of a surface layer portion of the non-element region of the gallium-based compound semiconductor layer; and annealing the gallium-based compound semiconductor layer.

An enhancement mode compound semiconductor field-effect transistor (FET) includes a source, a drain, and a gate located therebetween. The transistor further includes a first gallium nitride-based hetero-interface located under the gate and a buried region, located under the first hetero-interface, the buried p-type region configured to determine an enhancement mode FET turn-on threshold voltage to permit current flow between the source and the drain.

Methods of fabricating a semiconductor device include providing a semiconductor substrate that includes a plurality of epitaxial layers, including a channel layer and a permanent cap over the channel layer, where the permanent cap defines an upper surface of the semiconductor substrate, and forming a sacrificial cap over the permanent cap in an active region of the device, where the sacrificial cap comprises a semiconductor material that includes aluminum. The method also includes forming one or more current carrying regions (e.g., source and drain regions) in the semiconductor substrate in the active region of the device by performing an ion implantation process to implant ions through the sacrificial cap, and into the semiconductor substrate, completely removing the sacrificial cap in the active region of the device, while refraining from removing the permanent cap, and forming one or more current carrying contacts over the one or more current carrying regions.

The present disclosure provides a semiconductor device. The semiconductor device comprises a substrate, a plurality of isolation regions in the substrate and an active region surrounded by the isolation regions. A p-type doped region is interposed between two n-type doped regions in the substrate. A buried gate structure is formed in the substrate and disposed between the p-type doped region and the n-type doped region. The buried gate structure comprises a gate conductive material, a gate insulating layer disposed over the gate conductive material and a gate liner surrounding the gate conductive material and the gate insulating layer. A plurality of contact plugs are formed on the p-type doped region and the plurality of n-type doped regions.