| 摘要 |
PURPOSE:To obtain a sufficient operating margin by a method wherein the surface of a channel region for a memory transistor as a nonvolatile storage element is composed of an identical conductivity type whose concentration is lower than that of the surface of another channel region for a selective transistor or is composed of an opposite conductivity type. CONSTITUTION:A field oxide film 2 and a sacrifice oxide film 3 are formed on a silicon substrate 1. Then, source-drain regions 4 for a memory transistor and a channel region 5 for a selective transistor are formed. Then, an ion- implantation mask 6 is formed; arsenic is implanted; a channel region 7 is formed. Then, the film 3 is removed; a gate oxide film 8 is formed. Then, a tunnel oxide film 9 is formed. Then, a polysilicon oxide film 11 and a gate oxide film 12 are deposited. Then, gate electrodes for the memory transistor and the selective transistor are patterned by an RIE method by making use of a resist 13 as a mask. |
