Semiconductor device, and method for protecting low-k dielectric feature of semiconductor device

1. A semiconductor device, comprising:

a semiconductor feature; and

a first low-k dielectric feature formed on the semiconductor feature, and including a body portion and a surface portion,

wherein the surface portion conformally covers over the body portion, and contains silicon and at least one element that is contained in the body portion,

wherein the surface portion has a greater concentration of silicon than the body portion, and

wherein the surface portion is thinner than the body portion in a thickness direction.

2. The semiconductor device according to claim 1 , wherein the surface portion has a thickness in a range from 5 angstroms to 10 angstroms.

3. The semiconductor device according to claim 1 , wherein the body portion of the first low-k dielectric feature is made of BC x N y , where x is greater than or equal to zero, and y is a positive number.

4. The semiconductor device according to claim 3 , wherein the surface portion includes at least one of SiN, SiBCN or SiBN.

5. The semiconductor device according to claim 3 , wherein the first low-k dielectric feature further includes carbon, and the surface portion further contains carbon.

6. The semiconductor device according to claim 1 , wherein the surface portion includes at least one of SiN, SiBN, or SiBCN.

7. The semiconductor device according to claim 3 , wherein the surface portion further contains SiO 2 .

8. The semiconductor device according to claim 1 , further comprising:

a second low-k dielectric feature covering over the surface portion of the first low-k dielectric feature, and including a body portion and a surface portion,

wherein the surface portion of the second low-k dielectric feature contains silicon, has a greater concentration of silicon than the body portion of the second low-k dielectric feature, and covers over the body portion of the second low-k dielectric feature.

9. The semiconductor device according to claim 1 , wherein the surface portion of the first low-k dielectric feature is L-shaped.

10. The semiconductor device according to claim 1 , wherein the body portion of the first low-k dielectric feature includes carbon, boron and nitrogen, and the surface portion of the first low-k dielectric feature further contains carbon and one or both of boron and nitrogen.

11. The semiconductor device according to claim 1 , further comprising a second low-k dielectric feature disposed between the first low-k dielectric feature and the semiconductor feature, wherein the second low-k dielectric feature is of different chemical composition from the first low-k dielectric features.

12. The semiconductor device according to claim 1 , further comprising a second low-k dielectric feature formed on the semiconductor feature, and including a body portion and a surface portion;

wherein the surface portion conformally covers over the body portion, and contains silicon and at least one element that is contained in the body portion;

wherein the surface portion has a greater concentration of silicon than the body portion; and

wherein the surface portion is thinner than the body portion in a thickness direction;

wherein the body portion of the second low-k dielectric feature is spaced apart from the body portion of the first low-k dielectric feature.

13. The semiconductor device according to claim 12 , further comprising a silicon-containing feature that interconnects the surface portion of the second low-k dielectric feature and the surface portion of the first low-k dielectric feature.

14. A semiconductor device, comprising:

a semiconductor feature;

a pair of first low-k dielectric features formed on the semiconductor feature and spaced apart from each other;

a gate feature formed on the semiconductor feature and sandwiched between the first low-k dielectric features;

a gate dielectric formed between the gate feature and the first low-k dielectric features and between the gate feature and the semiconductor feature;

a Si-containing layer formed on a sidewall surface of the first low-k dielectric features that is opposite to the gate feature; and

a pair of source/drain features formed in the semiconductor feature and at opposite sides of the gate feature,

wherein the Si-containing layer is L-shaped, and has an end lower than a top surface of one of the source/drain features,

wherein the one of the source/drain features has a sidewall facing the other one of the source/drain features, and the end of the Si-containing layer is in contact with the sidewall of the one of the source/drain features, and

wherein the first low-k dielectric feature includes carbon, boron and nitrogen, and the Si-containing layer further contains carbon and one or both of boron and nitrogen.

15. The semiconductor device according to claim 14 , wherein the Si-containing layer is thinner than the first low-k dielectric features in a thickness direction.

16. The semiconductor device according to claim 14 , wherein the Si-containing layer further contains SiO 2 .

17. The semiconductor device according to claim 14 , further comprising a pair of second low-k dielectric features that are formed on the semiconductor feature, that sandwich the gate feature therebetween, and that are of different chemical composition from the first low-k dielectric features, wherein the Si-containing layer covers over both of the first low-k dielectric features and the second low-k dielectric features.

18. A semiconductor device, comprising:

a semiconductor feature;

a gate dielectric formed over the semiconductor feature;

a gate feature formed over the gate dielectric feature;

a pair of first low-k dielectric features that are respectively formed at opposite sides of the gate feature; and

a Si-containing layer conformally formed over the first low-k dielectric features,

wherein the first low-k dielectric features are made of BC x N y , where x is greater than or equal to zero, and y is a positive number,

wherein the Si-containing layer contains at least one of boron, carbon or nitrogen, and

wherein the semiconductor device further comprises a pair of second low-k dielectric features that are of different chemical composition from the first low-k dielectric features, each of the second low-k dielectric features being disposed between the Si-containing layer and a respective one of the first low-k dielectric features.

19. The semiconductor device according to claim 18 , wherein the first low-k dielectric features have a higher proportion of nitrogen than the second low-k dielectric features.

20. The semiconductor device according to claim 18 , wherein the Si-containing layer further contains SiO 2 .