Semiconductor device and method for fabricating the same

1. A method for fabricating a semiconductor device comprising:

forming a gate dielectric layer over a substrate;

forming an etch stop layer over the gate dielectric layer;

forming a sacrificial layer pattern over a second portion of the etch stop layer;

forming a first work function layer that covers a first portion of the etch stop layer and a sacrificial compound that covers the second portion of the etch stop layer;

exposing the second portion of the etch stop layer by removing the sacrificial compound; and

forming a second work function layer over the second portion of the etch stop layer and the first work function layer,

wherein the sacrificial compound is formed by a reaction between the sacrificial layer pattern and the first work function layer.

2. The method of claim 1 , wherein the forming of the first work function layer that covers the first portion of the etch stop layer and the sacrificial compound that covers the second portion of the etch stop layer includes:

forming a sacrificial layer over the etch stop layer;

removing the sacrificial layer over the first portion of the etch stop layer to form a sacrificial layer pattern over the second portion of the etch stop layer; and

forming the first work function layer over the sacrificial layer pattern and the first portion of the etch stop layer,

wherein the sacrificial layer pattern is transformed into the sacrificial compound while the first work function layer is formed over the first portion of the etch stop layer.

3. The method of claim 2 , wherein the sacrificial layer includes lanthanum oxide, and the sacrificial compound includes lanthanum chloride.

4. The method of claim 3 , wherein the first work function layer includes titanium nitride,

wherein the first work function layer is formed by using titanium tetrachloride (TiCl 4 ).

5. The method of claim 1 , wherein the first work function layer includes a titanium layer containing a first species, wherein the second work function layer includes a titanium layer containing a second species, and

wherein the second work function layer and the first work function layer have different work functions.

6. The method of claim 5 , wherein the first species includes nitrogen, and the second species includes aluminum, carbon, or a combination thereof.

7. The method of claim 1 , wherein the etch stop layer includes tantalum nitride.

8. The method of claim 1 , further comprising:

forming a capping layer over the gate dielectric layer, before the forming of the etch stop layer,

wherein the capping layer includes titanium nitride.

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

preparing a substrate including a first channel region and a second channel region;

forming an inter-layer dielectric layer over the substrate, wherein the inter-layer dielectric layer includes a first trench exposing the first channel region and a second trench exposing the second channel region;

forming a gate dielectric layer in the first trench and the second trench;

forming an etch stop layer over the gate dielectric layer;

forming a sacrificial layer pattern over the etch stop layer in the second trench;

forming a first work function layer over the etch stop layer in the first trench and forming a sacrificial compound over the etch stop layer in the second trench;

exposing the etch stop layer in the second trench by removing the sacrificial compound;

forming a second work function layer over the first work function layer in the first trench and over the etch stop layer in the second trench; and

forming a low resistivity layer over the second work function layer to fill the first trench and the second trench,

wherein the sacrificial compound is formed by a reaction between the sacrificial layer pattern and the first work function layer.

10. The method of claim 9 , wherein the forming of the first work function layer over the etch stop layer in the first trench and forming of the sacrificial compound over the etch stop layer in the second trench includes:

forming a sacrificial layer over the etch stop layer;

removing the sacrificial layer over the etch stop layer in the first trench to form a sacrificial layer pattern over the etch stop layer in the second trench; and

applying first work function material to the first and the second trenches to form the first work function layer over the etch stop layer in the first trench and to transform the sacrificial layer pattern in the second trench into the sacrificial compound.

11. The method of claim 10 , wherein the sacrificial layer includes lanthanum oxide, and the sacrificial compound includes lanthanum chloride.

12. The method of claim 11 , wherein the first work function layer includes titanium nitride, and

wherein the first work function material includes titanium tetrachloride (TiCl 4 ).

13. The method of claim 9 , wherein the first work function layer includes titanium nitride, and

wherein the second work function layer includes a titanium layer containing a second species, and

wherein the second species is suitable to make the second work function layer and the first work function layer have different work functions.

14. The method of claim 13 , wherein the species includes aluminum, carbon, or a combination thereof.

15. The method of claim 9 , further comprising:

forming a capping layer over the gate dielectric layer, before the forming of the etch stop layer,

wherein the capping layer includes titanium nitride.

16. The method of claim 9 , wherein the etch stop layer includes tantalum nitride.

17. The method of claim 9 , wherein the first work function layer is suitable to serve as a P-channel transistor, and the second work function layer is suitable to serve as an N-channel transistor.