FinFET and method for manufacturing the same

1. A method for manufacturing a FinFET, the method comprising:

forming a fin structure over a substrate;

depositing a dummy gate across over the fin structure;

forming a pair of first spacers on sidewalls of the dummy gate;

forming a pair of second spacers adjacent to the first spacers;

forming a source/drain region in the fin structure not covered by the dummy gate;

removing the dummy gate to expose the fin structure;

truncating the first spacers;

forming a contact etch stop layer over the source/drain region;

forming an interlayer dielectric layer over the contact etch stop layer; and

forming a gate stack covering the exposed fin structure and top surfaces of the first spacers.

2. The method of claim 1 , further comprising forming doped regions in the fin structure and adjacent to the dummy gate.

3. The method of claim 1 , wherein truncating the first spacers is performed by etching the first spacers to remove upper portions of the first spacers.

4. The method of claim 3 , wherein etching the first spacers is performed by oxygen ashing, oxygen and carbon tetrachloride ashing, or carbon monoxide ashing.

5. The method of claim 1 , further comprising:

truncating the second spacers; and

forming the gate stack covering top surfaces of the second spacers.

6. The method of claim 5 , wherein truncating the second spacers is performed by etching the second spacers to remove upper portions of the second spacers, and etching the second spacers is performed by oxygen ashing, oxygen and carbon tetrachloride (CF 4 ), or carbon monoxide ashing.

7. The method of claim 1 , wherein the first spacers are made of a material selected from the group consisting of low-k SiOC and SiOCN.

8. The method of claim 1 , wherein the contact etch stop layer comprises a material selected from a group consisting of silicon nitride, such as Si 3 N 4 , silicon oxy-nitride, silicon carbon nitride, and a combination thereof.

9. The method of claim 1 , wherein the first spacers are made of a material selected from the group consisting of low-k SiOC and SiOCN, and the second spacers are made of a material selected from the group consisting of SiN and SiCN.

10. A method for manufacturing a FinFET, the method comprising:

forming a dummy gate across over a fin structure;

forming a pair of first spacers on sidewalls of the dummy gate;

forming a pair of second spacers on sidewalls of the first spacers;

forming a recess in the fin structure and not covered by the dummy gate;

epitaxially growing a source/drain region in the recess;

removing the dummy gate to expose the fin structure;

removing upper portions of the first spacers;

forming a contact etch stop layer over the source/drain region;

forming a dielectric layer on the contact etch stop layer; and

forming a gate stack covering the exposed fin structure and top surfaces of the first spacers.

11. The method of claim 10 , further comprising removing upper portions of the second spacers.

12. The method of claim 10 , further comprising forming doped regions in the fin structure and adjacent to the dummy gate.

13. The method of claim 10 , wherein forming the gate stack comprises:

forming a gate dielectric layer covering the exposed fin structure and top surfaces of the first spacers; and

forming a gate electrode on the gate dielectric layer.

14. The method of claim 13 , wherein the gate electrode comprises a material selected from a group consisting of tungsten (W), titanium (Ti), tantalum (Ta), aluminum (Al), nickel (Ni), ruthenium (Ru), palladium (Pd), platinum (Pt), tungsten nitride (WNx), titanium nitride (TiN), tantalum nitride (TaN), aluminum nitride (AlN), tungsten silicide (WSix), nickel silicide (Ni 2 Si), titanium silicide (TiSi 2 ), titanium aluminide (TiAl), an alloy thereof, and a combination thereof.

15. The method of claim 13 , wherein the gate dielectric layer comprises a material selected from a group consisting of Al 2 O 3 , HfO 2 , ZrO 2 , La 2 O 3 , TiO 2 , SrTiO 3 , LaAlO 3 , Y 2 O 3 , Al 2 O x N y , HfO x N y , ZrO x N y , La 2 O x N y , TiO x N y , SrTiO x N y , LaAlO x N y , Y 2 O x N y , SiON, SiN x , a silicate, and a combination thereof.