Mos device having non-uniform dopant concentration and method for fabricating the same

Abstract

A metal-oxide-semiconductor (MOS) device in which the nonuniform dopant concentration in the channel region is obtained by means of ion implantation through a polysilicon gate electrode of nonuniform cross section, which is itself obtained by oxidizing the polysilicon using a semirecessed LOCOS process. The present invention is directed most generally to a semiconductor device which includes: a semiconductor substrate of a first conductivity type; a gate insulator on the substrate, the gate insulator sharing an interface with the substrate; a gate electrode on the gate insulator, the gate electrode having a first side, a second side, and a middle region between the first and second sides; a source doped region of a second conductivity type within the substrate to the first side of the gate electrode and a drain doped region of the second conductivity type within the substrate to the second side of the gate electrode, the source and drain doped regions self-aligned to the gate electrode; and a channel doped region of the first conductivity type within the substrate below the gate electrode, the channel doped region having a peak dopant concentration profile such that the peak dopant concentration under the middle region of the gate electrode occurs further below the gate insulator-substrate interface than does either the peak dopant concentration under the first side of the gate electrode or the peak dopant concentration under the second side of the gate electrode.