Metal oxide semiconductor field effect transistor for reducing resistance between source and drain and method for fabricating the same

A method for fabricating a MOS field effect transistor having a gate insulation layer and a gate electrode sequentially formed on a semiconductor substrate, the method comprising the steps of:

• forming first source/drain extension regions in the semiconductor substrate by implanting impurity ions using the gate electrode as an ion-implantation mask;
• forming first spacers on the sidewalls of the gate electrode and the gate insulation layer;
• forming second source/drain extension regions deeper than the first source/drain extension regions by performing impurity ion-implantation using the first spacers and the gate electrode as an ion-implantation mask;
• forming second spacers on outer walls of the first spacers;
• forming deep source/drain regions deeper than the second source/drain extension regions by performing impurity ion-implantation using the second spacers and the gate electrode as an ion-implantation mask;
• forming a first silicide layer portion having a first thickness in the upper portion of each of the deep source/drain regions;
• removing the second spacers to expose the surfaces of the second source/drain extension regions;
• and
• forming a second silicide layer portion having a second thickness less than the first thickness and extending from the first silicide layer portion into the upper portion of each of the exposed second source/drain extension regions.