Erasable and programmable nonvolatile semiconductor memory, semiconductor integrated circuit device having the semiconductor memory and method of manufacturing the semiconductor memory

Abstract

A nonvolatile semiconductor memory has memory cells (,) each having an insulated-gate FET that has an information storage part. A semiconductor region (,) is formed at the surface of a channel region of each memory cell. The semiconductor region has the same conductivity type as a channel conductivity type and functions to decrease the strength of an electric field at the surface of the channel region. If the insulated-gate FET is of an n-channel type, the semiconductor region is of an n-type. The semiconductor region suppresses threshold voltage variations among the insulated-gate FETs of the memory cells and prevents soft-writing in the memory cells.