Method for fabricating semiconductor device

A method for fabricating a semiconductor device, comprising:

• providing a first gate electrode and a second gate electrode on a substrate, the first gate electrode and the second gate electrode being formed in a first region and a second region of the substrate, respectively;
• forming a conductive buffer layer along sidewalls of the first gate electrode and the second gate electrode and on upper surfaces of the first gate electrode and second gate electrode;
• forming an upper buffer layer along the conductive buffer layer;
• forming a first mask pattern covering the first region of the substrate on the conductive buffer layer;
• and
• forming a first impurity region in the substrate at sides of the second gate electrode using the first mask pattern as a mask of an ion implantation process.