| 摘要 |
PURPOSE:To enable highly reliable writing and erasing operations by completely surrounding an impurity region of rewriting region with a field insulating film, conducting it with a crossunder diffused layer to hold the same potential, thereby preventing the deterioration in the characteristics of the informing rewriting region. CONSTITUTION:An n<+> type layer 23 held at the same potential as a source 22 is formed adjacent to a channel region, and a floating gate 25 is extended on the region. The second control gate 31 made of polycrystalline silicon or metal which is capacitively coupled to the gate 25 is formed by insulating them via gate insulating film 26, 30 separately from the first control gate 27. The periphery of a gate insulating film 29 on an n<+> type layer 28 of rewriting region is surrounded by a completely thick field insulating film 32. This layer 28 is conductecd with the source 22 via an n<+> type crossunder diffused layer 33 formed in advance under the layer 32. |
