Semiconductor device and method for fabricating the same

A method for fabricating a semiconductor device comprising:

• the step of forming a gate electrode having a gate length of below 50 nm including 50 nm over a semiconductor substrate;
• the step of forming a source/drain diffused layer in the semiconductor substrate on both sides of the gate electrode;
• the step of forming a cobalt film on the gate electrode;
• the first thermal processing step of reacting the cobalt film with the gate electrode to form a cobalt monosilicide film on an upper part of the gate electrode;
• the step of selectively etching off a part of the cobalt film, which has not reacted;
• and
• the second thermal processing step of reacting the cobalt monosilcide film with the gate electrode to form a cobalt disilicide film on the upper part of the gate electrode, wherein
• in the first thermal processing step, the cobalt monosilicide film is formed so that a ratio h/w of a height of the cobalt monosilicide film to a width of the cobalt monosilicide film is below 0.7 including 0.7.