Method of fabricating semiconductor device

A method of fabricating a semiconductor device, comprising:

• forming a plurality of semiconductor strips on a substrate;
• forming spacer films on the plurality of semiconductor strips, and performing a doping process on the spacer films;
• forming an interlayer dielectric layer aside the spacers films and on the plurality of semiconductor strips;
• performing a thermal treatment process on the plurality of semiconductor strips, the spacer films and the interlayer dielectric layer;
• and
• forming gate structures in between the spacer films.

A method of fabricating a semiconductor device, comprising:

• forming a plurality of semiconductor strips on a substrate, wherein each of the plurality of semiconductor strips comprises a channel region and source/drain regions;
• forming dummy gate structures on the channel region and spacer films aside the dummy gate structures, wherein the spacer films are doped with a dopant;
• and
• forming an interlayer dielectric layer on the plurality of semiconductor strips and aside the spacer films, wherein the spacer films comprises a first portion adjacent to sidewalls of the dummy gate structures and a second portion facing away from the sidewalls of the dummy gate structures, and a concentration of the dopant in the first portion varies from a concentration of the dopant in the second portion.