Method of making SRAM to improve interface state density utilizing PMOS TFT

Claim 1

A method of forming a SRAM memory cell comprising the steps of: forming a polysilicon film on a silicon oxide substrate by chemical vapor deposition; removing portions of the polysilicon film to form holes; implanting boron difluoride ions into the remaining portions of the polysilicon film to form a gate electrode and source and drain electrodes; forming a first silicon oxide insulation film on the gate electrode and source and drain electrodes by chemical vapor deposition; removing portions of the first silicon oxide film on the source and drain electrodes by photolithography and etching to form contact holes; forming an amorphous silicon film on the inside of the contact holes and the surface of the first silicon oxide insulation film; performing annealing treatment on said amorphous silicon film to convert said amorphous silicon film into a polysilicon film; removing portions of the polysilicon film with the remaining portions serving as an active region; oxidizing the active region at 850° C. to form a second silicon oxide film on the active region and simultaneously form a gate oxide film at the interface between the active region and the first silicon oxide film; forming source and drain regions adjacent opposing sides of the gate electrode by ion implantation of a p-conductivity type dopant; forming an interlayer insulation film on the surface of the second silicon oxide film; forming contact holes in the interlayer insulation film; implanting boron difluoride into the interlayer insulation film after formation of the contact holes; forming a metal wiring film on the inside of the contact holes and the surface of the interlayer insulation film; removing portions of the metal film; and depositing silicon nitride film by plasma enhanced chemical vapor deposition.

Claim 2

A method of forming a SRAM memory cell comprising the steps of: forming a polysilicon film on a silicon oxide substrate by chemical vapor deposition; removing portions of the polysilicon film to form holes; implanting boron difluoride ions into the remaining portions of the polysilicon film to form a gate electrode and source and drain electrodes; forming a first silicon oxide insulation film on the gate electrode and source and drain electrodes by chemical vapor deposition; removing portions of the first silicon oxide film on the source and drain electrodes by photolithography and etching to form contact holes; forming an amorphous silicon film on the inside of the contact holes and the surface of the first silicon oxide insulation film; performing annealing treatment on said amorphous silicon film to convert said amorphous silicon film into a polysilicon film; removing portions of the polysilicon film with the remaining portions serving as an active region; oxidizing the active region at 850° C. to form a second silicon oxide film on the active region and simultaneously form a gate oxide film at the interface between the active region and the first silicon oxide film; forming source and drain regions adjacent opposing sides of the gate electrode by ion implantation of a p-conductivity type dopant; forming an interlayer insulation film on the surface of the second silicon oxide film; forming contact holes in the interlayer insulation film; implanting boron difluoride into the interlayer insulation film after formation of the contact holes; forming a metal wiring film on the inside of the contact holes and the surface of the interlayer insulation film; removing portions of the metal film; and depositing silicon nitride film by plasma enhanced chemical vapor deposition.