NONVOLATILE SEMICONDUCTOR MEMORY AND FABRICATION THEREOF

摘要

PROBLEM TO BE SOLVED: To increase the yield by removing etching residues on the side wall at a step formed by an insulating film abutting on the side wall of a first gate layer and a first gate insulating film through isotropic etching thereby preventing short circuit between gates. SOLUTION: Floating gate layers 4, 9 are etched using a control gate electrode 17 as a mask to form a floating electrode 18. Etching residues of polysilicon are generated along the side wall of an etched central trench part. The etching residues are removed through isotropic etching corresponding to etching of a polisilicon film of 500Åthick using a down flow type etching system. Polysilicon residues are removed from the trench part of an insulation film using a fabrication method where isotropic etching is performed after forming a floating gate electrode and short circuit between gates can be prevented.