Patent ID: 6939802

Claim:
A method of manufacturing a semiconductor device comprising: laminating an insulating oxide film and a first poly-silicon film sequentially, in order, on a silicon layer of a first conductivity type; forming an opening by selectively etching said insulating oxide film and said first poly-silicon film and exposing a part of said silicon layer in the opening; forming an impurity doped region of a second conductivity type by implanting a dopant impurity producing the second conductivity type into the part of said silicon layer exposed in the opening; removing a natural oxidation film from said impurity doped region and said first poly-silicon film with hydrofluoric acid; forming a thin uniform thickness oxide film on said impurity doped region in the opening and on said first poly-silicon film from which the natural oxidation film has been removed; forming a second poly-silicon film covering said first poly-silicon film, including in the opening, and implanting the dopant impurity producing the second conductivity type in said second poly-silicon film; activating the impurity producing the second conductivity type and implanted in said second poly-silicon film, and diffusing the dopant impurity producing the second conductivity type into said first poly-silicon film through said thin uniform thickness oxide film; and forming openings in said thin uniform thickness oxide film by annealing at a temperature from about 950° C. to 1150° C. for a time period of at least ten seconds and up to about three minutes, thereby forming an electrical contact between said second poly-silicon film and said impurity doped region through said first poly-silicon film.