METHOD FOR MANUFACTURING MOS TRANSISTOR

PURPOSE: A fabrication of an MOS transistor is provided to improve a property and a reliability of an MOS transistor by preventing an generation of a compound by means of oxygen using an ammonium gas atmosphere during a formation process of a silicide layer. CONSTITUTION: After forming a gate(2) on a substrate(1), a region including a source/drain(3) of a low density and a source/drain(5) of a high density is formed on an under portion of the substrate of a side face of the gate to separate using a sidewall(4) each other. A Ni layer(6) is deposited on the source/drain of the high density and the gate, and An ion for preventing an oxygen reaction is implanted onto the deposited Ni layer. By annealing the substrate including the Ni layer under an inert gas atmosphere, a silicide layer(7) is formed for diffusing an Ni ion included in the Ni layer to the gate and the source/drain region of the high density, thereby forming an MOS transistor. The ion for preventing an oxygen reaction is a nitrogen ion.