A semiconductor device having a CMOS structure having a low resistivity silicide layer in a source/drain region is fabricated. To realize silicide formation for resistivity reduction of the n-type source/drain region, an impurity-free silicon layer is formed thereon before forming a high melting point metal silicide layer. For the n-type source/drain region, ion implantation is made through the silicon layer. It is thus possible to obtain a shallow junction of the p-type source/drain region, prevent ion implantation time increase and obtain quick fabrication without reducing the ion implantation energy.