| 摘要 |
PURPOSE:To reduce a stepwise difference on the surface of a substrate by a method wherein the first gate electrode is buried in a semiconductor substrate in the state that the electrode is covered with an insulation film, and the second gate electrode is formed on the first gate electrode, thus changing a semiconductor layer between both gate electrodes into a channel region. CONSTITUTION:The first gate electrode 15 composed of a polycrystalline Si covered with oxide Si films 12' and 12'' is formed on the Si substrate 11, and a polycrystalline Si layer 16 is formed on the surface. After forming element isolation layers 17 and a gate oxide film 18, the second gate electrode 19 is formed on the gate oxide film 18. The gate oxide film 18 is removed, a source region 20 and a drain region 21 are formed, and interlayer insulation films 23, wiring patterns 24, etc. are formed. When one of the two gate electrodes is a floating gate, and the other a control gate, the write voltage given to the control gate can be reduced, too. |
