A semiconductor device comprising a semiconductor substrate having a recess whose depth is not more than 6 nm, a source region and a drain region which are formed in a surface region of the semiconductor substrate so as to sandwich the recess, each of the source region and the drain region being constituted of an extension region and a contact junction region, a gate insulating film formed between the source region and the drain region in the semiconductor substrate, and a gate electrode formed on the gate insulating film.