| 摘要 |
PURPOSE:To improve characteristics to an electric field of an oxide film by forming an ion implantation layer having optimum concentration into a substrate sectin just under the thin oxide film shaped onto a drain region in an EEPROM having floating gate structure. CONSTITUTION:A gate oxide film 17 is formed in an element region in a silicon substrate 11 isolated by a field oxide film 15, one part of the oxide film 17 is removed, and an ion implantation layer 19 having acceleration voltage of 100keV or less and the quantity of a dose of 5X10<14>/cm<2>-5X10<15>/cm<2> is shaped from the removi section. A thin silicon oxide film 20 is formed onto the implantation layer through thermal oxidation, and a floating gate electrode 21, a gate oxide film 24 for a control gate electrode and a control gate electrode 25 are shaped onto the oxide film 20 in succession. Accordingly, the characteristics of the oxide film are improved, and durability to repeated wriring/erasing can be lengthened. |
