| 摘要 |
PURPOSE:To obtain a memory transistor adapted for high integration and large memory capacity by providing the step of forming the second gate electrode to cover through the third gate insulating film on the first gate electrode, thereby applying high speed and stable writing and erasing characteristics. CONSTITUTION:An insulator isolating field oxidized film 43 is formed on a main flat surface of a P type semiconductor substrate 42, a source 45 and a drain 44 are then formed, the first gate oxidized film 46 is then formed, and part of the film 46 is removed by etching. Then, after it is thermally oxidized so that the oxidized film is grown at the position where the N type semiconductor of the drain is exposed, an N type doped polycrystalline silicon film is formed to form the first gate electrode. Then, the third gate oxidized film 49 is formed, and the N type doped second polycrystalline silicon film 50 is formed. Further, the second gate electrode to cover through the third gate oxidized film on the first gate electrode is formed. |
