Nonvolatile semiconductor memory device and method of manufacturing the same

Using a rapid thermal oxidation device, the top and side surfaces of a floating gate electrode are oxidized by in situ steam generation (ISSG), wherein oxygen to which about 0.5 to 33% hydrogen has been added is introduced directly into a chamber with a temperature of approximately 900 to 1100 DEG C and a pressure of approximately 1,000 to 2,000 Pa, in order to generate water vapor from the introduced hydrogen and oxygen on a heated semiconductor substrate. Thus, an insulating film made of silicon oxide is formed on the surface of the floating gate electrode.