Semiconductor device and method of manufacturing the same

A semiconductor device manufacturing method comprising the steps of:

• forming a tunnel insulating film on a semiconductor substrate;
• forming a first semiconductor film constituting a lower portion of a floating gate on the tunnel insulating film;
• forming device isolation recesses by etching device isolation regions of the first semiconductor film, the tunnel insulating film, and the semiconductor substrate;
• forming a device isolation insulating film in the device isolation recesses and on the first semiconductor film;
• removing the device isolation insulating film from an area above the first semiconductor film and also thinning the device isolation insulating film above the device isolation recesses;
• growing selectively a second semiconductor film serving as an upper portion of the floating gate on the first semiconductor film and also growing the second semiconductor film on the device isolation insulating film to extend in a lateral direction from the device isolation insulating film;
• forming a dielectric film on the floating gate;
• and
• forming a conductive film serving as a control gate on the dielectric film.