Patent ID: 8125012

Claim:
A non-volatile semiconductor storage device including a memory transistor and a select transistor and having a split-gate configuration, the storage device comprising: (a) first and second semiconductor regions formed in a semiconductor substrate, the first semiconductor region being a source region, and the second semiconductor region being a drain region; (b) a first electric conductor and a second electric conductor both formed above a part of the semiconductor substrate that is between the first and second semiconductor regions, the first electric conductor being a control gate electrode of the select transistor, and the second electric conductor being a memory gate electrode of the memory transistor; (c) a first insulating film formed between the first electric conductor and the semiconductor substrate; and (d) a second insulating film formed between the second electric conductor and the semiconductor substrate, wherein the second insulating film includes a first potential barrier film formed on the semiconductor substrate, an electric charge holding film formed above the first potential barrier film, and a second potential barrier film formed above the electric charge holding film, wherein the non-volatile semiconductor storage device writes information by injecting electrons into the electric charge holding film and erases the information by injecting holes into the electric charge holding film, and wherein the electric charge holding film includes: a first silicon nitride film consisting of silicon and nitrogen and containing a stoichiometrically excessive amount of silicon, and a second silicon nitride film formed on the first silicon nitride film and consisting of silicon and nitrogen of a stoichiometric ratio.