A gate oxide film (23), a gate electrode (24) and a gate cap insulating film (25) are stacked on an active region of a p-type semiconductor substrate (21), and an insulating side wall (29) is formed, followed by BF2 ion implantation. Thus, a surface of the p-type semiconductor substrate becomes amorphous so that single-crystal silicon is prevented from epitaxially growing in the next process of depositing polysilicon (33). Halo regions (32) are formed using the BF2 ions having the opposite conductivity to a source/drain to reduce the short-channel effect. The substrate is then passed through a nitrogen purge chamber having a dew point kept at −100° C. to remove water molecules completely, and polysilicon (33) is deposited. Because native oxide is prevented from growing at an interface between the active region and the polysilicon, source/drain regions (34) formed later by implantation and diffusion of n-type impurity ions achieve a uniform junction depth.