Semiconductor device and method of fabricating the same

A method of fabricating a semiconductor device comprising:

• depositing a polycrystalline silicon germanium film above a semiconductor substrate with a gate dielectric film sandwiched therebetween;
• patterning said polycrystalline silicon germanium film to form gate electrodes in first and second circuit regions, respectively;
• before or after patterning of said gate electrodes, selectively oxidizing a surface of the polycrystalline silicon germanium film in the second circuit region such that a germanium concentration of the polycrystalline silicon germanium film in the second circuit region is higher than a germanium concentration of the polycrystalline silicon germanium film of the first circuit region and such that a thickness of polycrystalline silicon germanium film in the second circuit region is smaller than a thickness of polycrystalline silicon germanium film in the first circuit region;
• forming first diffusion layers in source and drain regions by impurity ion implantation with said gate electrodes as a mask;
• forming sidewall dielectric films on lateral walls of said gate electrodes;
• letting a silicon layer selectively grow on surfaces of said gate electrodes and of said first diffusion layers;
• forming a metal silicide film on said silicon layer overlying said gate electrodes and said source and drain regions;
• and
• performing impurity ion implantation with said gate electrodes and said sidewall dielectric films as a mask to thereby form in said source and drain regions second diffusion layers greater than said first diffusion layers both in depth and in concentration.

A method of fabricating a semiconductor device comprising:

• depositing a polycrystalline silicon germanium film above a semiconductor substrate with a gate dielectric film sandwiched therebetween;
• patterning said polycrystalline silicon germanium film to thereby form gate electrodes in first and second circuit regions, respectively;
• before or after patterning of said gate electrodes, selectively oxidizing a surface of the polycrystalline silicon germanium film in the second circuit region such that a germanium concentration of the polycrystalline silicon germanium film in the second circuit region is higher than a germanium concentration of the polycrystalline silicon germanium film of the first circuit region and such that a thickness of polycrystalline silicon germanium film in the second circuit region is smaller than a thickness of polycrystalline silicon germanium film in the first circuit region;
• forming first sidewall dielectric films on lateral walls of said gate electrodes;
• letting a silicon layer selectively grow on said gate electrodes and surfaces of source/drain regions;
• performing impurity ion implantation with said gate electrodes and said first sidewall dielectric films as a mask to thereby form first diffusion layers in said source/drain regions;
• performing, after removal of said first sidewall dielectric films, impurity ion implantation with said gate electrodes as a mask to thereby form in said source/drain regions second diffusion layers less in depth and concentration than said first diffusion layers;
• forming second sidewall dielectric films on the lateral walls of said gate electrodes;
• and
• forming a metal silicide film on said gate electrodes and a surface of said silicon layer in said source/drain regions.