Semiconductor device and method for manufacturing same

1. A method for manufacturing a semiconductor device, comprising:

forming a fin in an upper surface of a semiconductor substrate to extend in a first direction;

forming a mask film to cover the fin;

making a plurality of first trenches in the mask film to extend in a second direction intersecting the first direction to reach the fin;

filling sidewall members into the first trenches, the sidewall members being insulative;

making a second trench by removing the mask film from a portion of a space between the sidewall members;

forming a gate insulating film on a surface of a first portion of the fin disposed inside the second trench;

forming a gate electrode on the gate insulating film inside the second trench to extend in the second direction to straddle the first portion;

making a third trench by removing the mask film from the remaining space between the sidewall members; and

causing a second portion of the fin disposed inside the third trench to become a conductor.

2. The method according to claim 1 , wherein

a cross section of a configuration of the fin has an inverted T-shaped configuration, and an upper portion of the fin is finer than a lower portion of the fin in the forming of the fin, and

the upper portion and two side portions of the lower portion are caused to become conductors in the causing of the second portion to become the conductor,

the method further comprising:

causing the upper portion and the two side portions of the lower portion of the first portion to become oxide films by performing an oxidation treatment between the making of the second trench and the forming of the gate insulating film; and

removing the oxide film between the making of the second trench and the forming of the gate insulating film.

3. The method according to claim 1 , wherein

a cross section of a configuration of the fin has an inverted T-shaped configuration, and an upper portion of the fin is finer than a lower portion of the fin in the forming of the fin, and

the upper portion and two side portions of the lower portion are caused to become conductors in the causing of the second portion to become the conductor,

the method further comprising performing isotropic etching of the first portion between the making of the second trench and the forming of the gate insulating film.

4. The method according to claim 1 , wherein

the making of the first trenches includes:

forming a non-doped film on the mask film;

forming a core member on the non-doped film to extend in the second direction;

forming sidewall hard masks on two side surfaces of the core member;

causing a portion of the non-doped film including a region directly under one of a pair of the sidewall hard masks formed on the two side surfaces of the core member to become an impurity-doped film by implanting an impurity into the non-doped film from a direction tilted toward one first-direction side with respect to an upward perpendicular direction using a structural body made of the core member and the pair of the sidewall hard masks as a mask;

removing the core member; and

selectively removing the mask film by performing anisotropic etching using the sidewall hard masks as a mask,

the making of the second trench includes:

removing the non-doped film without removing the impurity-doped film; and

removing a portion of the mask film positioned in a region directly under the non-doped film, and

the making of the third trench includes:

removing the impurity-doped film; and

removing a portion of the mask film positioned in a region directly under the impurity-doped film.

5. The method according to claim 4 , wherein

the non-doped film is formed of non-doped silicon, and

the impurity is boron.

6. The method according to claim 5 , wherein

the removing of the non-doped film includes an alkali treatment, and

the removing of the impurity-doped film includes performing anisotropic etching.

7. The method according to claim 1 , wherein the mask film is formed of carbon.

8. The method according to claim 1 , wherein

the semiconductor substrate includes silicon, and

the causing to become the conductor is performed by siliciding.

9. A method for manufacturing a semiconductor device, comprising:

forming a fin in an upper surface of a semiconductor substrate to extend in a first direction, a cross section of the fin having an inverted T-shaped configuration, an upper portion of the fin being finer than a lower portion of the fin;

removing the upper portion and two side portions of the lower portion of a first portion of the fin;

forming a gate insulating film on a surface of the first portion;

forming a gate electrode on the gate insulating film to extend in a second direction intersecting the first direction to straddle the first portion; and

causing the upper portion and the two side portions of the lower portion of a second portion of the fin separated from the first portion in the first direction to become conductors.

10. The method according to claim 9 , further comprising:

forming a mask film to cover the fin;

making a plurality of first trenches in the mask film to extend in the second direction to reach the fin;

filling sidewall members into the first trenches, the sidewall members being insulative;

making a second trench by removing the mask film from a portion of a space between the sidewall members; and

making a third trench by removing the mask film from the remaining space between the sidewall members,

the first portion being disposed inside the second trench,

the removing, the forming of the gate insulating film, and the forming of the gate electrode being implemented between the making of the second trench and the making of the third trench,

the second portion being disposed inside the third trench, and

the causing to become the conductors being implemented after the making of the third trench.

11. The method according to claim 10 , wherein the mask film is formed of carbon.

12. The method according to claim 9 , wherein the removing includes:

causing the upper portion and the two side portions of the lower portion of the first portion to become oxide films by performing an oxidation treatment; and

removing the oxide film.

13. The method according to claim 9 , wherein the removing includes performing isotropic etching of the first portion.

14. The method according to claim 9 , wherein

the semiconductor substrate includes silicon, and

the causing to become the conductor is performed by siliciding.

15. A semiconductor device, comprising:

a semiconductor substrate, a fin being formed in an upper surface of the semiconductor substrate to extend in a first direction;

a gate electrode extending in a second direction intersecting the first direction to straddle a first portion of the fin;

a gate insulating film disposed between the first portion and the gate electrode; and

a conductive layer covering a second portion of the fin separated from the first portion in the first direction,

the conductive layer including:

a base portion disposed on a side surface of the second portion; and

a protruding portion disposed in a region directly above the second portion to protrude upward from the base portion,

a width of the protruding portion being finer than a width of the base portion in a cross section perpendicular to the first direction,

an upper end of the first portion of the fin and an upper end of the second portion of the fin being positioned lower than an upper end of a portion of the fin excluding the first portion and the second portion.

16. The device according to claim 15 , wherein

the semiconductor substrate includes silicon, and

the conductive layer is a silicide layer.