| 摘要 |
PURPOSE:To improve endurance characteristics and breakdown characteristics of a tunnel insulating film by partially setting the impurity concentration of a floating gate in contact with the tunnel insulating film low. CONSTITUTION:A second poly-Si film 8 containing an impurity in high concentration is formed so as to be electrically connected to a poly-Si film 5 on the top face of a water, a second poly-Si film 8 is oxidized through thermal oxidation to shape an insulating film 9, and a third poly-Si film 10 is formed onto the insulating film 9. A second poly-Si film 8a as a floating gate, the third poly-Si film 10 as a control gate, the insulating film 9 and a second poly-Si film 8b are shaped. Since the concentration of the impurity of the first poly-Si film 5 is lowered, the state in which the impurity is difficult to be introduced into a film 4 having three layer structure is brought. Accordingly, endurance characteristics and the insulation breakdown characteristic of a tunnel insulating film can be improved. |
