| 摘要 |
When the surfaces of a selection gate electrode and a floating gate electrode are thermally oxidized with the selection gate electrode disposed below the floating gate electrode, the thickness of a gate oxide film formed on the selection gate electrode can be made larger than that of a gate oxide film formed on the other portion. As a result, the coupling ratio of a memory transistor can be increased. Thus, the coupling ratio can be adequately increased by partly increasing the thickness of the insulation film between the floating gate electrode and the semiconductor substrate.
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