Semiconductor device and manufacturing method thereof

A method for manufacturing a semiconductor device, comprising the steps of:

• forming an insulating film on an entire surface of a substrate having a device isolation region and a first and a second conductive region;
• forming a semiconductor device structure having a gate electrode forming region on each of the conductive regions, the insulating film being disposed between the gate electrode forming region and each of the conductive regions;
• forming a gate electrode groove in the gate electrode forming region of the semiconductor device structure, wherein the insulating film is removed in the gate electrode groove;
• depositing a gate insulating film and a film of metal gate electrode material on a bottom surface and a side surface of the gate electrode groove;
• forming a first alloy by alloying the film of metal gate electrode material disposed in a gate electrode groove of the first conductive region;
• and
• forming a second alloy different from the first alloy by alloying the film of metal gate electrode material disposed in a gate electrode groove of the second conductive region.