A low resistance Co silicide layer with less leakage current is formed over the surface of the source and drain of a MISFET by optimizing the film forming conditions and annealing conditions upon formation of Co (cobalt) silicide. More specifically, a low resistance source and drain (n.sup.+ type semiconductor regions, p.sup.+ type semiconductor regions) with less junction leakage current are formed, upon formation of a Co silicide layer by heat treating a Co film deposited over the source and drain (n.sup.+ type semiconductor regions, p.sup.+ type semiconductor regions) of the MISFET, by depositing the Co film at a temperature as low as 200.degree. C. or less, carrying out heat treatment in three stages to convert the Co silicide layer from a dicobalt silicide (Co.sub.2Si) layer to a cobalt monosilicide (CoSi) layer and, then, to a cobalt disilicide (CoSi.sub.2) layer, successively.