Semiconductor device MOSFET with V-shaped drain contact

Claim 1

A metal oxide semiconductor field effect transistor formed on a semiconductive substrate of a first conductivity type having a surface, said transistor comprising: (a) a conductive gate electrode layer insulatively provided above said substrate; (b) first and second semiconductive layers of a second conductivity type, which are formed in the surface of said substrate to serve as source and drain regions of said transistor, said substrate having first and second concave portions formed to have inner surfaces and bottom portions, said first and second concave portions being adjacent to said first and second semiconductive layers, respectively and said first and second semiconductive layers including contact portions which extend below the bottom portions of said first and second concave portions to surround said first and second concave portions, respectively; (c) an insulative layer formed on said substrate defining therein contact holes for said source and drain regions; (d) first and second conductive wiring layers which are formed on said insulative layer to cover said contact holes in such a manner that they are electrically in contact with said first and second semiconductive layers through said concave portions, respectively; and (e) third and fourth semiconductive layers of the first conductivity type, which are formed in said substrate to surround said contact portions of said first and second semiconductive layers, respectively, for suppressing current charges from leaking from said first and second concave portions, thereby preventing the occurrence of punch-through phenomenon in said transistor, said third and fourth semiconductive layers being formed by doping inpurities of the first conductivity type in said substrate through said contact holes.