Semiconductor devices having gate structures with skirt regions

1. 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.

2. The semiconductor device of claim 1 , wherein a 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.

3. The semiconductor device of claim 1 , further comprising a dummy gate structure extending in the second direction, to cross the first active fin, the first active fin having an end in the first direction under the dummy gate structure, wherein the dummy gate structure is spaced apart from the first gate structure in the first direction, and

wherein the dummy gate structure includes a fifth skirt where a first side of the dummy gate structure facing the first side of the first gate structure extends outwardly in the first direction to contact the side surface of the first active fin and a sixth skirt where the first side of the dummy gate structure extends outwardly in the first direction to contact the side surface of the second active fin.

4. The semiconductor device of claim 3 , wherein an outer surface of the fifth skirt has a fourth concave profile at a lower half portion of the dummy gate structure in the vertical plane,

wherein the outer surface of the fifth skirt has a fifth concave profile in the horizontal plane, and

wherein an entirety of the fifth skirt having the fourth concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above the surface of the substrate.

5. The semiconductor device of claim 3 , wherein a second side of the dummy gate structure, which is opposite the first side of the dummy gate structure, is a planar side surface that does not include any skirt.

6. The semiconductor device of claim 3 , further comprising a device isolation layer that extends in the second direction and is contact with the end of the first active fin,

wherein the dummy gate structure is on the first active fin and the device isolation layer.

7. The semiconductor device of claim 1 , further comprising a second gate structure extending in the second direction, wherein the second gate structure is spaced apart from the first gate structure, and

wherein the second gate structure includes a seventh skirt where a first side of the second gate structure facing the second side of the first gate structure extends outwardly in the first direction to contact a side surface of the first active fin and an eighth skirt where the first side of the second gate structure extends outwardly in the first direction to contact the side surface of the second active fin.

8. The semiconductor device of claim 7 , wherein each of outer surfaces of the seventh and eighth skirts has the first concave profile at a lower half portion of the second gate structure in the vertical plane,

wherein each of the outer surfaces of the seventh and eighth skirts has the second concave profile in the horizontal plane, and

wherein an entirety of the seventh skirt having the first concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above the surface of the substrate.

9. The semiconductor device of claim 7 , wherein a distance between the first gate structure and the second gate structure in the first direction increases from the side surface of the first active fin to a region between the first active fin and the second active fin.

10. 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.

11. The semiconductor device of claim 10 , 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.

12. The semiconductor device of claim 10 , wherein the first gate structure further includes 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.

13. The semiconductor device of claim 10 , further comprising a dummy gate structure extending in the second direction, to cross the first active fin, the first active fin having an end in the first direction under the dummy gate structure, wherein the dummy gate structure is spaced apart from the first gate structure in the first direction, and

wherein the dummy gate structure includes a fifth skirt where a first side of the dummy gate structure facing the first side of the first gate structure extends outwardly in the first direction to contact the side surface of the first active fin, and a sixth skirt where the first side of the dummy gate structure extends outwardly in the first direction to contact the side surface of the second active fin.

14. The semiconductor device of claim 13 , wherein an outer surface of the fifth skirt has a fourth concave profile at a lower half portion of the dummy gate structure in the vertical plane,

wherein the outer surface of the fifth skirt has a fifth concave profile in the horizontal plane, and

wherein an entirety of the fifth skirt having the fourth concave profile in the vertical plane continuously decreases in width, in the first direction, with increasing height above the surface of the substrate.

15. The semiconductor device of claim 10 , further comprising a second gate structure extending in the second direction, wherein the second gate structure is spaced apart from the first gate structure,

wherein the second gate structure includes a seventh skirt where a first side of the second gate structure facing a second side of the first gate structure extends outwardly in the first direction to contact a side surface of the first active fin and an eighth skirt where the first side of the second gate structure extends outwardly in the first direction to contact the side surface of the second active fin.

16. 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.

17. The semiconductor device of claim 16 , wherein 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.

18. The semiconductor device of claim 16 , further comprising a second gate structure extending in the second direction, wherein the second gate structure is spaced apart from the first gate structure,

wherein the second gate structure includes a fifth skirt where a first side of the second gate structure facing the second side of the first gate structure extends outwardly in the first direction to contact a side surface of the first active fin and a sixth skirt where the first side of the second gate structure extends outwardly in the first direction to contact the side surface of the second active fin.

19. The semiconductor device of claim 18 , wherein a distance between the first gate structure and the second gate structure in the first direction increases from the side surface of the first active fin to a region between the first active fin and the second active fin.