Method for fabricating semiconductor device

A method for fabricating a MOSFET device comprising the steps of:

• forming a sacrificial gate on an active region of a silicon substrate;
• forming a source/drain region on the active regions of the silicon substrate at sides of the sacrificial gate;
• forming a first interlayer insulating film on the silicon substrate while exposing the sacrificial gate;
• removing the exposed sacrificial gate to form a groove;
• forming a gate insulating film and a tungsten film over the silicon substrate;
• polishing the tungsten film and the gate insulating film to form a tungsten gate in the groove;
• forming a polysilicon film over the resultant substrate including the tungsten gate;
• forming a tungsten silicide film self-aligned at an interface between the polysilicon film and the tungsten gate;
• polishing the polysilicon film and the tungsten silicide to expose the first interlayer insulating film;
• forming a second interlayer insulating film over the silicon substrate;
• forming a contact hole exposing the source/drain region by etching a predetermined parts of the first and second interlayer insulating films;
• conducting of oxidization process such that if a portion of the tungsten suicide film is exposed, a silicon oxide film is formed on the exposed portion;
• and
• forming a contact plug within the contact hole.