Semiconductor memory device and method for manufacturing the same

A semiconductor memory device comprising:

• a semiconductor substrate;
• a first insulating film formed on the semiconductor substrate, and including a silicon oxynitride film and a silicon oxide film formed on the silicon oxynitride film, the silicon oxynitride film having a stacked structure formed with a first silicon oxynitride layer, a silicon nitride layer and a second silicon oxynitride layer in order, a total film thickness of the silicon oxide film and the second silicon oxynitride layer being equal to or greater than a value obtained by dividing binding energy of silicon and hydroxyl by an electric field across the first insulating film while erasing it and an elementary electric charge;
• a charge storage layer formed on the first insulating film;
• a second insulating film formed on the charge storage layer;
• and
• a control gate formed on the second insulating film.

A method for manufacturing a semiconductor memory device, comprising:

• placing a semiconductor substrate into a first atmosphere, thereby forming a nitride film above a surface of the semiconductor substrate, the first atmosphere containing a first nitriding gas nitriding the surface of the semiconductor substrate and a first diluent gas not substantially reacting with the semiconductor substrate during manufacture, the ratio of the sum of the partial pressure of the first diluent gas and the partial pressure of the first nitriding gas to the partial pressure of the first nitriding gas being 5 or higher, and the total pressure of the atmosphere being 40 Torr or lower;
• placing the semiconductor substrate having the nitride layer formed above the surface thereof into a second atmosphere, thereby forming a first oxynitride layer between the semiconductor substrate and the nitride layer, and a second oxynitride layer on a surface of the nitride layer, the second atmosphere containing an oxidizing gas and a second diluent gas not substantially reacting with the semiconductor substrate during manufacture;
• and
• depositing an oxide film on the second oxynitride layer by CVD, thereby forming a tunnel insulating film having a stacked structure formed with the first oxynitride layer, the nitride layer, the second oxynitride layer, and the oxide film in order.