Semiconductor devices having gate structures with skirt regions

A semiconductor device comprising:

• a first active fin protruding from a substrate and extending in a first direction;
• a second active fin protruding from the substrate and extending in the first direction, wherein the second active fin is spaced apart from the first active fin in a second direction that intersects the first direction;
• and
• a first gate structure extending in the second direction, the first gate structure includes a gate insulation layer, a work function control layer on the gate insulation layer and a conductive layer on the work function control layer,
• wherein the first gate structure includes a first skirt where a first side of the first gate structure extends outwardly in the first direction to contact a side surface of the first active fin, a second skirt where a second side of the first gate structure, which is opposite the first side of the first gate structure, extends outwardly in the first direction to contact the side surface of the first active fin, a third skirt where the first side of the first gate structure extends outwardly in the first direction to contact a side surface of the second active fin, and a fourth skirt where the second side of the first gate structure extends outwardly in the first direction to contact the side surface of the second active fin,
• wherein each of outer surfaces of the first skirt, the second skirt, the third skirt, and the fourth skirt has a first concave profile at a lower half portion of the first gate structure in a vertical plane,
• wherein each of the outer surfaces of the first skirt, the second skirt, the third skirt, and the fourth skirt has a second concave profile in a horizontal plane,
• wherein an entirety of the first skirt having the first concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above a surface of the substrate,
• wherein the entirety of the first skirt having the second concave profile in the horizontal plane continuously increases in width, in the first direction, with decreasing distance to the side surface of the first active fin,
• wherein the first skirt includes the gate insulation layer and the work function control layer, an outer surface of the gate insulation layer of the first skirt has the first concave profile in the vertical plane, and an outer surface of the work function control layer of the first skirt has a third concave profile in the vertical plane,
• wherein an entirety of the work function control layer of the first skirt having the third concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above the surface of the substrate, and
• wherein the second concave profile in the horizontal plane converges with the first concave profile in the vertical plane.

A semiconductor device comprising:

• a first active fin protruding from a substrate and extending in a first direction;
• a second active fin protruding from the substrate and extending in the first direction, wherein the second active fin is spaced apart from the first active fin in a second direction that intersects the first direction;
• and
• a first gate structure extending in the second direction, the first gate structure includes a gate insulation layer, a work function control layer on the gate insulation layer and a conductive layer on the work function control layer,
• wherein the first gate structure includes a first skirt where a first side of the first gate structure extends outwardly in the first direction to contact a side surface of the first active fin,
• wherein an outer surface of the first skirt has a first concave profile at a lower half portion of the first gate structure in a vertical plane,
• wherein the outer surface of the first skirt has a second concave profile in a horizontal plane,
• wherein an entirety of the first skirt having the first concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above a surface of the substrate,
• wherein the first skirt includes the gate insulation layer and the work function control layer, an outer surface of the gate insulation layer of the first skirt has the first concave profile in the vertical plane, and an outer surface of the work function control layer of the first skirt has a third concave profile in the vertical plane,
• wherein an entirety of the work function control layer of the first skirt having the third concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above the surface of the substrate, and
• wherein the second concave profile in the horizontal plane converges with the first concave profile in the vertical plane.

A semiconductor device comprising:

• a first active fin protruding from a substrate and extending in a first direction;
• a second active fin protruding from the substrate and extending in the first direction, wherein the second active fin is spaced apart from the first active fin in a second direction that intersects the first direction;
• and
• a first gate structure extending in the second direction,
• wherein the first gate structure includes a first skirt where a first side of the first gate structure extends outwardly in the first direction to contact a side surface of the first active fin, a second skirt where a second side of the first gate structure, which is opposite the first side of the first gate structure, extends outwardly in the first direction to contact the side surface of the first active fin, a third skirt where the first side of the first gate structure extends outwardly in the first direction to contact a side surface of the second active fin, and a fourth skirt where the second side of the first gate structure extends outwardly in the first direction to contact the side surface of the second active fin,
• wherein each of outer surfaces of the first skirt, the second skirt, the third skirt, and the fourth skirt has a first concave profile at a lower half portion of the first gate structure in a vertical plane,
• wherein each of the outer surfaces of the first skirt, the second skirt, the third skirt, and the fourth skirt has a second concave profile in a horizontal plane,
• wherein an entirety of the first skirt having the first concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above a surface of the substrate,
• wherein the entirety of the first skirt having the second concave profile in the horizontal plane continuously increases in width, in the first direction, with decreasing distance to the side surface of the first active fin,
• wherein the second concave profile in the horizontal plane converges with the first concave profile in the vertical plane, and
• wherein a first width of the first gate structure in the first direction decreases from the side surface of the first active fin to a region between the first active fin and the second active fin.