A semiconductor device and a method of forming the same are provided. In an embodiment, an exemplary semiconductor device includes a vertical stack of channel members disposed over a substrate, a gate structure wrapping around each channel member of the vertical stack of channel members, and a source/drain feature disposed over the substrate and coupled to the vertical stack of channel members. The source/drain feature is spaced apart from a sidewall of the gate structure by an air gap and a dielectric layer, and the air gap extends into the source/drain feature.

A semiconductor device includes a substrate including first and second regions, first and second active patterns provided on the first and second regions, respectively, a pair of first source/drain patterns on the first active pattern and a first channel pattern therebetween, a pair of second source/drain patterns on the second active pattern and a second channel pattern therebetween, first and second gate electrodes respectively provided on the first and second channel patterns, and first and second gate insulating layers respectively interposed between the first and second channel patterns and the first and second gate electrodes. Each of the first and second gate insulating layers includes an interface layer and a first high-k dielectric layer thereon, and the first gate insulating layer further includes a second high-k dielectric layer on the first high-k dielectric layer.

An integrated circuit (IC) device includes a conductive region including a first metal on a substrate. An insulating film is on the conductive region. A conductive plug including a second metal passes through the insulating film and extends in a vertical direction. A conductive barrier pattern is between the conductive region and the conductive plug. The conductive barrier pattern has a first surface in contact with the conductive region and a second surface in contact with the conductive plug. A bottom surface and a lower sidewall of the conductive plug are in contact with the conductive barrier pattern, and an upper sidewall of the conductive plug is in contact with the insulating film. The conductive barrier pattern includes a vertical barrier portion between the insulating film and the conductive plug, and the vertical barrier portion has a width tapering along a first direction away from the conductive region.

A wide band gap semiconductor device includes a semiconductor layer, a trench formed in the semiconductor layer, first, second, and third regions having particular conductivity types and defining sides of the trench, and a first electrode embedded inside an insulating film in the trench. The second region integrally includes a first portion arranged closer to a first surface of the semiconductor layer than to a bottom surface of the trench, and a second portion projecting from the first portion toward a second surface of the semiconductor layer to a depth below a bottom surface of the trench. The second portion of the second region defines a boundary surface with the third region, the boundary region being at an incline with respect to the first surface of the semiconductor layer.

An SiC semiconductor device includes an SiC semiconductor layer including an SiC monocrystal that is constituted of a hexagonal crystal and having a first main surface as a device surface facing a c-plane of the SiC monocrystal and has an off angle inclined with respect to the c-plane, a second main surface at a side opposite to the first main surface, and a side surface facing an a-plane of the SiC monocrystal and has an angle less than the off angle with respect to a normal to the first main surface when the normal is 0°.

A semiconductor device includes a region of semiconductor material of a first conductivity type. A body region of a second conductivity type is in the region of semiconductor material. The body region includes a first segment with a first peak dopant concentration, and a second segment laterally adjacent to the first segment with a second peak dopant concentration. A source region of the first conductivity type is in the first segment but not in at least part of the second segment. An insulated gate electrode adjoins the first segment and is configured to provide a first channel region in the first segment, adjoins the second segment and is configured to provide a second channel region in the second segment, and adjoins the source region. During a linear mode of operation, current flows first in the second segment but not in the first segment to reduce the likelihood of thermal runaway.

In a first vertical field-effect transistor in which first source regions and first connectors each of which electrically connects a first body region and a first source electrode are alternately and periodically disposed in a first direction (Y direction) in which a first trench extends, a ratio of LS [μm] to LB [μm] is at least 1/7 and at most 1/3, where LS denotes a length of one of the first source regions in the first direction, and LB denotes a length of one of the first connectors in the first direction, and LB≤−0.024×(VGS).sup.2+0.633×VGS−0.721 is satisfied for a voltage VGS [V] of a specification value of a semiconductor device, the voltage VGS being applied to a first gate conductor with reference to an electric potential of the first source electrode.

A semiconductor device may include a substrate including a first cell region, a second cell region, and a dummy region between the first and second cell regions, and conductive patterns included in the first cell region, the second cell region, and the dummy region. A first pattern density, which is defined as a density of the conductive patterns of the first cell region, may be different from a second pattern density, which is defined as a density of the conductive patterns of the second cell region. A third pattern density, which is defined as a density of the conductive patterns of the dummy region, gradually changes in a region between the first cell region and the second cell region. A top surface of the substrate may be inclined at an angle, in the dummy region.

A semiconductor device includes a gate structure extending from a first surface of a semiconductor portion into a mesa section between neighboring field electrode structures and an alignment layer formed on the first surface. The alignment layer includes mask pits formed in the alignment layer in a vertical projection of the field electrode structures. Sidewalls of the mask pits have a smaller tilt angle with respect to the first surface than sidewalls of the field electrode structures. The gate structure is in the vertical projection of a gap between neighboring mask pits.

A normally-off HEMT transistor includes a heterostructure including a channel layer and a barrier layer on the channel layer; a 2DEG layer in the heterostructure; an insulation layer in contact with a first region of the barrier layer; and a gate electrode through the whole thickness of the insulation layer, terminating in contact with a second region of the barrier layer. The barrier layer and the insulation layer have a mismatch of the lattice constant (“lattice mismatch”), which generates a mechanical stress solely in the first region of the barrier layer, giving rise to a first concentration of electrons in a first portion of the two-dimensional conduction channel which is under the first region of the barrier layer which is greater than a second concentration of electrons in a second portion of the two-dimensional conduction channel which is under the second region of the barrier layer.