Patent ID: 7294551

Claim:
A method for manufacturing a semiconductor device comprising a high concentration source region of a second conductive type formed adjacent to one end of a gate electrode which is formed on a first conductive type semiconductor substrate via a gate oxide film, a low concentration drain region of the second conductive type formed near another end of the gate electrode, and a high concentration drain region formed in the low concentration drain region such that the low concentration drain region extends beneath the entire high concentration drain region and the high concentration drain region is laterally spaced away from the gate electrode, wherein a forming process of said low concentration drain region comprises: ion-implanting at least two kinds of second conductive type impurities, each of said impurities having a diffusion coefficient different from each other, through the same mask, wherein the mask prevents ion-implantation of the at least two kinds of second conductive type impurities in the source region; and diffusing said impurities.