When Ti as a barrier metal layer is brought into contact with a diffusion region of boron provided on a surface of a silicon substrate, there is a problem that boron is absorbed by titanium silicide, and contact resistance is increased. Although there is a method of additionally implanting boron whose amount is equal to the amount of boron absorbed by titanium silicide, there has been a problem that when boron is additionally implanted into, for example, a source region in a p-channel type, the additionally added boron is diffused deeply at the diffusion step, and characteristics are deteriorated. According to the invention, after formation of an element region, boron is additionally implanted into the whole surface at a dosage of about 10% of an element region, and is activated in the vicinity of a surface of a silicon substrate by an alloying process of a barrier metal layer. By this, a specified concentration profile of the element region is kept, and the impurity concentration only in the vicinity of the surface can be raised. Accordingly, even if boron is absorbed by titanium silicide, a specified boron concentration can be kept in the element region, and the increase of contact resistance can be suppressed.