Patent ID: 7919806

Claim:
A nonvolatile semiconductor memory device, comprising: a memory transistor including a channel formation region defined between two source and drain regions formed on a semiconductor substrate, a bottom insulating film, a charge storage film and a top insulating film formed in order at least on said channel formation region, said charge storage film having a charge storage function, and a gate electrode formed on said top insulating film; said bottom insulating film being formed from a plurality of films containing nitrogen such that the content of nitrogen of a lowermost one of said films which contacts with said channel formation region and an uppermost one of said films which contacts with said gate electrode is higher than that of the other one or ones of said films which exist between the uppermost and lowermost films, wherein a barrier energy of said bottom insulating film with respect to silicon is lower than that of silicon oxide with respect to silicon, wherein said channel formation region has, at least on one side at least of the two source and drain regions, a high concentration channel region which has a conduction type the same as that of said channel formation region and has a concentration higher than that in the other region.