Patent ID: 8053826

Claim:
A method of manufacturing a non-volatile semiconductor memory device comprising the steps of: (a) forming a tunnel silicon oxide film on a semiconductor substrate; (b) converting a part of the tunnel silicon oxide film in contact with the semiconductor substrate to a silicon oxynitride film after the step (a); (c) forming a charge storage film on the tunnel silicon oxide film; (d) forming a gate insulating film on the charge storage film; (e) forming a conductive film on the gate insulating film; (f) forming a gate electrode by patterning the conductive film and processing the gate insulating film, the charge storage film, the tunnel silicon oxide film, and the silicon oxynitride film in conformity with the gate electrode; and (g) forming a source region and a drain region of the non-volatile semiconductor memory device, wherein the step (b) includes the steps of: (b1) introducing nitrogen atoms into an interface of the semiconductor substrate and the tunnel silicon oxide film by a first thermal treatment in an atmosphere containing nitrogen monoxide; and (b2) diffusing the nitrogen atoms in a film-thickness direction of the tunnel silicon oxide film to form the silicon oxynitride film after the step (b1) by a second thermal treatment in an atmosphere containing oxygen.