<p>PURPOSE: A method for forming a MOS transistor is provided to prevent a short channel effect by increasing the effective length of a gate. CONSTITUTION: A gate structure (108) is formed on a semiconductor substrate. A conformal first spacer layer (110) is formed on the surface of a gate structure and the semiconductor substrate. A second spacer layer is formed on the first spacer layer. A second spacer (112a) is formed on the first spacer layer. An impurity implantation process is performed on the semiconductor substrate to form a source/drain extension region (114).</p>
