Mos structure with precisely controlled channel length and method

Claim 1

In an MOS semiconductor structure, a body formed of a semiconductor material of one conductivity type, said body having a planar surface, a first diffused region of opposite conductivity type formed in said body and extending to said surface and forming a first PN junction in said body which on said surface forms a first continuous line which encloses an area on the surface, a second diffused region in said body of said one conductivity type disposed within said first region and forming a source, said second diffused region forming a second PN junction which extends to the surface, said second PN junction forming a second continuous line on said surface within said first continuous line which encloses an area which is less than the area enclosed by said first continuous line, said second diffused region being formed so that said second continuous line has a general contour with a key which extends out of the general contour, said first and second PN junctions being spaced so that there is provided therebetween a channel region of said opposite conductivity type of precise width which extends to the surface, said channel region including a keylike region that extends into said source and extends to said surface, a layer of insulating material disposed on said surface and overlying said first and second PN junctions and the portions of the channel region extending to the surface, metallization formed on the insulaTing layer and forming a gate contact, metallization disposed on said surface making contact with the region inside said second diffusion to form a source contact and making contact to the keylike region so that the channel is shorted to the source, and means making contact to said surface in the region outside of said first diffused region to form a drain contact.