Method of manufacturing a semiconductor device having non-volatile memory cell portion with single transistor type memory cells and peripheral portion with misfets

Abstract

A method of manufacturing a semiconductor memory device having nonvolatile memory cells each formed of a MISFET having both a floating gate and a control gate and first and second semiconductor regions. By this method, an impurity, for example, arsenic, is introduced to form both the first and second semiconductor regions but, however, a lower dose of arsenic is introduced in the formation of the second semiconductor region. The first semiconductor region is formed to have a junction depth greater than that of the second semiconductor region, and both the first and second semiconductor regions have portions thereof extending under the floating gate electrode. Carriers stored in the floating gate electrode are transferred between the floating gate electrode and the first semiconductor region by tunneling through the insulating film beneath the floating gate electrode. The method further features the formation of MISFETs of peripheral circuits.