Patent ID: 7682990

Claim:
A method of manufacturing a nonvolatile semiconductor memory device, comprising the steps of: forming a gate insulating film on a semiconductor substrate; forming a first gate electrode film on a top of the gate insulating film and forming an insulating film on a top of the first gate electrode film; selectively patterning the gate insulating film, the first gate electrode film and the insulating film to form a first gate section; forming a first insulating film on one side of the gate section and on the surface of the semiconductor substrate proximate the one side; selectively patterning a stack film to form a second gate section, the stack film being fabricated by forming a silicon nitride film on a top of the first insulating film, oxidizing a surface portion of the silicon nitride film so as to form a second insulating film having a thickness of at least 4 nm, and further forming a second gate electrode film on a top of the second insulating film; and forming a first impurity introducing layer on one side of the first gate section within the semiconductor substrate and forming a second impurity introducing layer on one side of the second gate section, by selectively introducing impurities by use of the first gate section and the second gate section as masks for the impurity introduction, wherein the second insulating film is a film formed by oxidizing the surface of the silicon nitride film with radical oxygen in absence of hydrogen with a thermal process, wherein the radical oxygen is generated from ozone being 20% or more in concentration, and wherein arrival time of the ozone from an ozone inlet to an area above the substrate is shorter than time for thermal decomposition of the ozone.