Semiconductor device having contact plugs and method of forming the same

1. A semiconductor device, comprising:

a first fin active area;

a second fin active area substantially parallel to the first fin active area;

a first source/drain in the first fin active area;

a second source/drain in the second fin active area;

a first contact plug on the first source/drain; and

a second contact plug on the second source/drain, wherein the second contact plug is only on one source/drain corresponding to the second source/drain and wherein a center of the second contact plug is offset from a center of the second source/drain.

2. The semiconductor device as claimed in claim 1 , wherein a bottom of the second contact plug has a different inclination from a bottom of the first contact plug.

3. The semiconductor device as claimed in claim 1 , further comprising:

an inclined interface between the second contact plug and the second source/drain, the inclined interface at a higher level in a direction approaching the first fin active area and at a lower level in a direction away from the first fin active area.

4. The semiconductor device as claimed in claim 1 , wherein a distance between a vertical center of the first contact plug and a vertical center of the second contact plug is greater than a distance between a vertical center of the first source/drain and a vertical center of the second source/drain.

5. The semiconductor device as claimed in claim 1 , wherein a lower end of the second contact plug is at a lower level than a lower end of the first contact plug.

6. The semiconductor device as claimed in claim 1 , wherein:

a horizontal width of the first source/drain is greater than a horizontal width of the first fin active area, and

a horizontal width of the second source/drain is greater than a horizontal width of the second fin active area.

7. The semiconductor device as claimed in claim 1 , wherein a farthest point of an interface between the second contact plug and the second source/drain from a vertical line passing through a center of the first source/drain is at a lower level than a closest point of the interface between the second contact plug and the second source/drain to the vertical line passing through the center of the first source/drain.

8. The semiconductor device as claimed in claim 1 , further comprising:

a third fin active area substantially parallel to the second fin active area;

a third source/drain in the third fin active area; and

a third contact plug on the third source/drain, wherein the second fin active area is between the first fin active area and the third fin active area, and wherein a center of the third contact plug is offset from a center of the third source/drain.

9. A semiconductor device, comprising:

first and second pull-up transistors;

first and second pull-down transistors;

first and second access transistors;

a first contact plug adjacent to the second pull-up transistor; and

a second contact plug adjacent to the second pull-down transistor, wherein a first source/drain in a first fin active area of the second pull-up transistor is connected to the first contact plug, a second source/drain in a second fin active area of the second pull-down transistor is connected to the second contact plug, and a center of the second contact plug is offset from a center of the second source/drain.

10. The semiconductor device as claimed in claim 9 , wherein the second fin active area is substantially parallel to the first fin active area.

11. The semiconductor device as claimed in claim 9 , wherein:

the first source/drain includes P-type impurities, and

the second source/drain includes N-type impurities.

12. The semiconductor device as claimed in claim 9 , wherein:

the first source/drain includes a crystal-growth SiGe layer, and

the second source/drain includes a crystal-growth Si layer, a crystal-growth SiC layer, or a combination thereof.

13. The semiconductor device as claimed in claim 9 , a distance between a vertical center of the first contact plug and a vertical center of the second contact plug is greater than a distance between a vertical center of the first source/drain and a vertical center of the second source/drain.

14. The semiconductor device as claimed in claim 9 , further comprising:

a third contact plug adjacent to the first pull-down transistor,

wherein a third source/drain in a third fin active area of the first pull-down transistor is connected to the third contact plug, and a center of the third contact plug is offset from a center of the third source/drain.

15. A semiconductor device, comprising:

a first source/drain area;

a second source/drain area;

a first contact plug on the first source/drain area; and

a second contact plug on the second source/drain area, wherein a center of the second contact plug is offset from a center of the second source/drain, wherein a farthest point of an interface between the second contact plug and the second source/drain area from a vertical line passing through the center of the first source/drain area is at a lower level than a closest point of the interface between the second contact plug and the second source/drain area to the vertical line passing through the center of the first source/drain area.

16. The semiconductor device as claimed in claim 15 , wherein the first contact plug is adjacent the second contact plug.

17. The semiconductor device as claimed in claim 15 , wherein:

the center of the first contact plug is spaced from the center of the second contact plug by a first distance;

the center of the first source/drain area is spaced from the center of the second source/drain area by a second distance; and

the first distance is greater than the second distance.

18. The semiconductor device as claimed in claim 15 , wherein a lower surface of the second contact plug is inclined.

19. The semiconductor device as claimed in claim 15 , wherein:

a lower surface of the first contact plug has a first shape;

a lower surface of the second contact plug has a second shape; and

the first shape is different from the second shape.

20. The semiconductor device as claimed in claim 15 , further comprising:

a third source/drain area; and

a third contact plug on the third source/drain area,

wherein the second source/drain area is between the first source/drain area and the third source/drain area, and a center of the third contact plug is offset from a center of the third source/drain area.