Patent ID: 8067809

Claim:
A method for fabricating a semiconductor storage device that operates by transferring a charge through a gate insulating film formed between a semiconductor substrate and a gate electrode, comprising: forming an oxide film on said semiconductor substrate; introducing an oxynitriding species previously diluted by plasma excitation gas, into a plasma processing apparatus; generating the oxynitriding species by a plasma; forming an oxynitride film on said semiconductor substrate as said gate insulating film by performing plasma oxynitridation with the oxynitriding species on the oxide film, the plasma oxynitridation forming nitrogen peaks at an interface between the semiconductor substrate and the gate insulating film and forming nitrogen peaks at an interface between the gate insulating film and the gate electrode, such that the nitrogen peaks at the interface between the semiconductor substrate and the gate insulating film are between 0.02 to 0.5 atomic %; introducing a nitriding species into the plasma processing apparatus; and enlarging the nitrogen peaks at the interface between the gate insulating film and the gate electrode by performing plasma nitridation processing with the nitriding species on said gate insulating film, after forming said oxynitride film, such that the nitrogen peaks at the interface between the gate insulating film and the gate electrode are between 0.02 to 0.5 atomic %, wherein said oxynitriding species contains NO gas at a ratio of 0.00001 to 0.01% to the total volume of gas introduced into said plasma processing apparatus.