A trench-type MESFET includes an n-type semiconductor layer including a Ga.sub.2O.sub.3-based single crystal and including plural trenches opening on one surface, first insulators respectively buried in bottom portions of the plural trenches, gate electrodes respectively buried in the plural trenches so as to be placed on the first insulators and so that side surfaces thereof are in contact with the n-type semiconductor layer, a source electrode connected to a mesa-shaped portion between the adjacent trenches of the n-type semiconductor layer, second insulators respectively buried in the plural trenches so as to be placed on the gate electrodes to insulate the gate electrodes and the source electrode, and a drain electrode directly or indirectly connected to the n-type semiconductor layer on a side opposite to the source electrode.

A nitride semiconductor device having a field effect gate is disclosed. The disclosed nitride semiconductor device includes a high-resistance material layer including a Group III-V compound semiconductor, a first channel control layer on the high-resistance material layer and including a Group III-V compound semiconductor of a first conductivity type, a channel layer on the channel layer control layer and including a nitride semiconductor of a second conductivity type opposite to the first conductivity type, and a gate electrode having a contact of an ohmic contact type with the first channel control layer.

A semiconductor device structure comprises a region of semiconductor material comprising a first conductivity type, a first major surface, and a second major surface opposite to the first major surface. A first trench gate structure includes a first trench extending from the first major surface into the region of semiconductor material, a first dielectric structure is over sidewall surfaces and a portion of a lower surface of the first trench, wherein the first dielectric structure comprises a first opening adjacent to the lower surface of the first trench, a first recessed contact extends through the first opening, and a first contact region is over the first recessed contact within the first trench, wherein the first recessed contact and the first contact region comprise different materials. A first doped region comprising a second dopant conductivity type opposite to the first conductivity type is in the region of semiconductor material and is spaced apart from the first major surface and below the first trench. A gate contact region is in the region of semiconductor material and is electrically connected to the first doped region.

A field effect transistor according to the present invention includes a semiconductor layer including a groove, an insulating film formed on an upper surface of the semiconductor layer and having an opening above the groove and a gate electrode buried in the opening to be in contact with side surfaces and a bottom surface of the groove and having parts being in contact with an upper surface of the insulating film on both sides of the opening, wherein the gate electrode has a T-shaped sectional shape in which a width of an upper end is larger than a width of the upper surface of the insulating film.

A semiconductor device includes a semiconductor layer provided on a substrate and including a channel layer, a source region connected to the channel layer and having a sheet resistance smaller than a sheet resistance of the channel layer, a drain region connected to the channel layer and having a sheet resistance smaller than the sheet resistance of the channel layer, a plurality of gates provided between the source region and the drain region, arranged in a direction intersecting an arrangement direction of the source region and the drain region, and embedded from an upper surface of the semiconductor layer to at least the channel layer, wherein a part of the source region has a convexity that faces a region between two adjacent gates among the plurality of gates, and protrudes toward a part of the drain region through the region between the two adjacent gates.

Forming an ohmic contact sealing layer disposed at an intersection between a sidewall of an ohmic contact and a surface of a semiconductor; forming an ohmic contact sealing layer on the intersection between a sidewall of the ohmic contact and the surface of the semiconductor; and subjecting the semiconductor with the ohmic contact to a chemical etchant.

A semiconductor device structure comprises a region of semiconductor material comprising a first conductivity type, a first major surface, and a second major surface opposite to the first major surface. A first trench gate structure includes a first trench extending from the first major surface into the region of semiconductor material, a first dielectric structure is over sidewall surfaces and a portion of a lower surface of the first trench, wherein the first dielectric structure comprises a first opening adjacent to the lower surface of the first trench, a first recessed contact extends through the first opening, and a first contact region is over the first recessed contact within the first trench, wherein the first recessed contact and the first contact region comprise different materials. A first doped region comprising a second dopant conductivity type opposite to the first conductivity type is in the region of semiconductor material and is spaced apart from the first major surface and below the first trench. A gate contact region is in the region of semiconductor material and is electrically connected to the first doped region.

This invention concerns a gate structure and a process for its manufacturing. In particular, the present invention concerns the gate structuring of a field effect transistor with reduced thermo-mechanical stress and increased reliability (lower electromigration or diffusion of the gate metal). The gate structure according to the invention comprises a substrate; an active layer disposed on the substrate; an intermediate layer disposed on the active layer, the intermediate layer-having a recess extending through the entire intermediate layer towards the active layer; and a contact element which is arranged within the recess, the contact element completely filling the recess and extending to above the intermediate layer, the contact element resting at least in sections directly on the intermediate layer; the contact element being made of a Schottky metal and the contact element having an interior cavity completely enclosed by the Schottky metal.

A semiconductor device structure includes a region of semiconductor material comprising a first conductivity type, an active region, and a termination region. A first active trench structure is disposed in the active region, and a second active trench structure is disposed in the active region and laterally separated from the first active trench by an active mesa region having a first width. A first termination trench structure is disposed in the termination region and separated from the second active trench by a transition mesa region having a second width and a higher carrier charge than that of the active mesa region. In one example, the second width is greater than the first width to provide the higher carrier charge. In another example, the dopant concentration in the transition mesa region is higher than that in the active mesa region to provide the higher carrier charge. The semiconductor device structure exhibits improved device ruggedness including, for example, improve unclamped inductive switching (UIS) performance.

Forming an ohmic contact sealing layer disposed at an intersection between a sidewall of an ohmic contact and a surface of a semiconductor; forming an ohmic contact sealing layer on the intersection between a sidewall of the ohmic contact and the surface of the semiconductor; and subjecting the semiconductor with the ohmic contact to a chemical etchant.