Patent ID: 6596590
Filing Date: 2003-07-22
Classification: G11C,H01L

Abstract:
A method of producing nonvolatile semiconductor memory devices which store multi-bit digital data of at least 2 bits therein, the method comprising:forming a multi-layer film suitably arranged for storage of the multi-bit digital data by successively depositing a first insulating film, a first dielectric film working as an electric charge accumulation layer, a second insulating film, a second dielectric film working as an electric charge accumulation layer, a third insulating film, a third dielectric film working as an electric charge accumulation layer, and a fourth insulating film on a predetermined region on a semiconductor substrate; forming an electrically multi-layer film on said multi-layer film and forming a resist thereon in the shape of a gate electrode; forming an electric charge-capturing film and a gate electrode in the shape of said resist by removing said multi-layer film and said electrically conducting layer by using said resist as a mask; and forming a source region and a drain region by adding impurities having a type of electric conduction opposite to that of said semiconductor substrate to a surface region of said semiconductor substrate by using said resist as a mask.