METHOD FOR FABRICATING A SEMICONDUCTOR DEVICE INCLUDING A MOS TRANSISTOR HAVING A SILICIDE LAYER

A method for fabricating a MOS transistor includes: forming a gate dielectric material layer over a substrate; forming a lower gate electrode material layer over the gate dielectric material layer; performing a first ion bombardment process of bombarding the lower gate electrode material layer with first ions; forming an intermediate gate electrode material layer including an amorphous silicon layer over the lower gate electrode material layer; forming an upper gate electrode material layer over the intermediate gate electrode material layer; performing a second ion bombardment process for bombarding the upper gate electrode material layer with second ions; and forming silicide layers in the lower gate electrode material layer and the upper gate electrode material layer to form a lower gate electrode layer and an upper gate electrode layer.