| 摘要 |
PURPOSE:To make the titled device to correspond to voltage applied on rewriting work rapidly, and to hold written contents stably by interposing an insulating film displaying current characteristics depending upon the direction of applied voltage between a floating gate and a drain high-concentration impurity region. CONSTITUTION:A LOCOS region 29 and a protective film 21 are formed to a P-type silicon substrate 20, an opening is bored to one part of the protective film 21 and a thin oxide film 22 is shaped through thermal oxidation, and an impurity is introduced to an oxide film 22 section while using a resist 28 as a mask. The concentration distribution of the impurity in the thin insulating film 22 is increased with an approach to an N<+> region 23 formed to the surface of the semiconductor substrate and made the highest in a section brought into contact with the N<+> region 23 by selecting energy on the implantation of ions within the extent of a projection range at that time. A floating gate 24, an insulating film 25, a control gate 26, a gate electrode 27, N<+> regions 23a-23c as a source or a drain, Al wirings, etc. are shaped. Accordingly, memory contents can be rewritten at low voltage, and written contents can be held stably. |
