Method of manufacturing a semiconductor memory device

A method of manufacturing a nonvolatile semiconductor memory device containing a select MOS transistor and a data storage MOS transistor, comprising the steps of:

• forming a first region by implanting impurities of a second conductivity type into an element region of a semiconductor substrate of a first conductivity type;
• forming a first insulating film in said element region;
• removing said first insulating film on said first region and a region adjacent to said first region;
• forming a second insulating film thicker than said first insulating film on said semiconductor substrate exposed in said element region;
• forming a first conducting film on said first and second insulating films;
• forming a hole in a position of said first conducting film;
• forming a third insulating film on first conductive film and in the hole;
• forming a second conducting film on said third insulating film;
• etching said second conducting film, said third insulating film, said first conducting film, said second insulating film, and said first insulating film in sequence, so as to form a gate electrode of said select MOS transistor and a control gate electrode and a floating-gate electrode of said data storage MOS transistor, said control gate electrode and said floating-gate electrode having a first portion and a second portion above said element region, said first portion being placed above said first region, and said first portion and said second portion being spaced apart on said element region and connected to each other on a field region;
• and
• implanting impurities of a second conductivity type into said element region with the gate electrode of said select MOS transistor and the control gate electrode and floating-gate electrode of said data storage MOS transistor as a mask, so as to form a second region in said element region between said first portion and said second portion and a third region in said element region between said first portion and the gate electrode of said select MOS transistor.