Method for forming a mos device with self-compensating v.sub.t -implants

Abstract

The present invention provides a method for forming a MOS device having self-compensating threshold adjust implants and reduced junction capacitance. A semiconductor substrate of a first conductivity type is provided. A gate oxide is formed on the surface of the semiconductor substrate, and a polysilicon gate is formed on the surface of the gate oxide. A first implant of a dopant of the first conductivity type is performed so as to form self-compensating implant regions in the semiconductor substrate on opposite sides of the gate. Disposable sidewall spacers are then formed around the polysilicon gate. A second implant of a dopant of a second conductivity type is performed so as to create highly-doped source/drain regions which are self-aligned to the sidewall spacers. The substrate with self-compensating implant regions and the highly-doped source/drain regions is then subject to a rapid thermal anneal (RTA) process so as to activate the dopant in the self-compensating implant regions and the highly-doped source/drain regions. The dopant within the self-compensating regions diffuses laterally under the polysilicon gate to define pockets. Thereafter, the disposable sidewall spacers are removed. Finally, a third implant of a dopant of the second conductivity type is performed so as to create lightly-doped source/drain regions in the self-compensating implant regions on opposite sides of the gate.