Abstract: A method of preventing diffusion penetration of the dopant used to dope polysilicon gate material in a MOSFET is disclosed. Atomic nitrogen is introduced into the substrate prior to gate oxide growth. The nitrogen later diffuses upward into the gate oxide and blocks subsequent ion implanted gate dopants from penetrating to the substrate. Low dosages of atomic nitrogen implantation, while not significantly affecting gate oxide growth rate, produce significant improvements in the damage immunity of thin gate oxides.

Abstract: The invention is directed to a process for forming p.sup.+ and n.sup.+ gates on a single substrate. A polycrystalline silicon or amorphous silicon layer is formed on a substrate with n-type and p-type regions formed therein and with a layer of silicon dioxide formed thereover and the structure is subjected to a low temperature anneal. A layer of metal silicide is then formed over the structure and n-type and p-type dopants are implanted into the resulting structure. A nitrogen implant is performed after the n-type dopant is implanted into the structure. The nitrogen implant reduces the amount to which the p-type dopant diffuses through the silicide layer and into the n.sup.+ gates. A dielectric material is then formed over the structure and patterned, after which the structure is subjected to additional processing steps to form gate stacks over the n-regions and the p-regions of the substrate.