| 摘要 |
PURPOSE:To increase the breakdown strength between a first gate electrode and a second gate electrode, by stacking in order a second gate insulating film and a second polysilicon film, after a side wall composed of insulator is formed on the side surface part of a first polysilicon film and the insulating film. CONSTITUTION:By dry-etching an oxide film 25, and by further dry-etching a first polysilicon film 24a, a first gate electrode 24 is formed. By CVD method, an insulating film 27 is stacked on the oxide film 25 and the exposed part of a first gate oxide film 23. The insulating film 27 and the first gate oxide film 23 are subjected to dry etching in the manner in which a side wall 28 is left on the step-difference side surface of the first gate electrode 24. By CVD method, a second gate oxide film 29 is grown on the side surface of the side wall 28 and the exposed part of a P-type silicon substrate. By stacking a second polysilicon layer 30a on the oxide film 29, and adding phosphorus of high concentration to the silicon layer 30a, a second gate electrode 30 is formed, thereby increasing the breakdown strength between the first gate electrode 24 and the second gate electrode 30. |
