Nonvolatile semiconductor memory device and manufacturing method therefor

Abstract

A nonvolatile semiconductor memory device including at least one MOS transistor in a peripheral circuit comprises a semiconductor substrate, isolation insulating films for defining a plurality of element formation regions, each of the isolation insulating films being buried in an isolation trench provided in the semiconductor substrate, a floating gate provided in each of the element formation regions via a first gate insulating film, a control gate provided on the floating gate via a second gate insulating film, and source and drain regions provided in the semiconductor substrate in self-alignment with the control gate, wherein the floating gate is self-aligned at an isolation end in a direction of a channel width, and comprises a plurality of polysilicon films.