Semiconductor device and method of fabricating the same

1. A method for forming a trench of a semiconductor device, the method comprising:

etching an oxide layer to form a trench therein;

conformally forming a first reaction layer along a surface of the trench, the first reaction layer including a first region on an upper portion of the trench and a second region on a lower portion of the trench;

forming a barrier layer by reacting a first amount of etching gas with the first region of the first reaction layer; and

etching the oxide layer on a lower portion of the second region by reacting a second amount of etching gas with the second region of the first reaction layer, the second amount of etching gas being greater than the first amount of etching gas.

2. The method of claim 1 , wherein the conformally forming forms the first reaction layer including NH 3 .

3. The method of claim 1 , wherein the etching gas includes at least one of HF and HF 3 .

4. The method of claim 3 , wherein the etching the oxide layer on a lower portion of the second region comprises etching the oxide layer using the etching gas including at least one of an inert gas, N 2 and NH 3 .

5. The method of claim 1 , wherein the forming a barrier layer comprises forming the barrier layer at a lower pressure than the etching the oxide layer on a lower portion of the second region.

6. The method of claim 1 , wherein the conformally forming forms the first reaction layer on a top surface of the oxide layer.

7. The method of claim 6 , wherein the forming a barrier layer forms the barrier layer on the top surface of the oxide layer.

8. The method of claim 1 , wherein prior to the etching an oxide layer to form a trench therein, further comprising:

forming a gate structure on a substrate;

forming a source/drain on at least one side of the gate structure; and

forming the oxide layer covering the substrate and the gate structure,

wherein the trench is formed on the source/drain.

9. The method of claim 8 , further comprising:

forming a fin between the substrate and the gate structure.

10. The method of claim 8 , wherein

the etching an oxide layer to form a trench therein comprises exposing a top surface of the source/drain having a natural thin film formed thereon, and

the etching an oxide layer on a lower portion of the second region comprises exposing the top surface of the source/drain by removing the natural thin film.

11. The method of claim 10 , wherein the natural thin film is an oxide layer.

12. The method of claim 10 , after the etching an oxide layer on a lower portion of the second region, further comprising:

forming a contact in the trench.

13. A method for fabricating a semiconductor device, the method comprising:

etching an insulation layer to form a trench therein, the insulation layer including a first region and a second region;

conformally forming a first reaction layer along a surface of the insulation layer;

forming a barrier layer by reacting an etching gas with the first reaction layer on a top surface of the first region, the first region being etched to a first thickness; and

etching the second region to a second thickness greater than the first thickness by reacting the etching gas with the first reaction layer on a top surface of the second region.

14. The method of claim 13 , wherein the etching an insulation layer etches an oxide layer.

15. The method of claim 13 , wherein

etching the second region includes using a first amount of the etching gas and a first pressure of the etching gas; and

forming a barrier layer includes using a second amount of the etching gas and a second pressure of the etching gas, the second amount and the second pressure less than the first amount and the first pressure.

16. A method for forming a trench of a semiconductor device, the method comprising:

etching an insulation layer to form a trench therein, the insulation layer including a first region and a second region;

conformally forming a first reaction layer along a surface of the trench;

forming a barrier layer by reacting a first amount of etching gas at a first pressure with the first reaction layer on a top surface of the first region; and

etching the insulation layer by reacting a second amount of etching gas at a second pressure with the first reaction layer on a top surface of the second region, the second pressure being less than the first pressure and the second amount of etching gas being greater than the first amount of etching gas.

17. The method of claim 16 , wherein the etching an insulation layer etches an oxide layer.

18. The method of claim 16 , wherein the conformally forming forms the first reaction layer including NH 3 .

19. The method of claim 16 , wherein the etching gas includes at least one of HF and HF 3 .

20. The method of claim 16 , wherein prior to the etching an insulation layer to form a trench therein, further comprising:

forming a gate structure on a substrate;

forming a source/drain on at least one side of the gate structure; and

forming the insulation layer covering the substrate and the gate structure,

wherein the trench is formed on the source/drain.