Nonvolatile semiconductor memory device and a method of the same

A nonvolatile semiconductor for memory device, including plural memory cells which each comprise a field effect transistor comprising:

• a first gate insulator film which is formed over a main face of a semiconductor substrate of a first conductivity type;
• a selector gate which is formed over the first gate insulator film and has side faces and a top face covered with a first insulator film;
• one out of floating gates which are formed, in a side-wall form, over both sides of the selector gate and are electrically separated from the selector gate by the first insulator film, wherein the gate length of the floating gate is shorter than the gate length of the selector gate in each of the transistor,
• a second gate insulator film formed to cover the surface of the floating gate and having portions being contact with the surface of the substrate;
• and
• a control gate which is formed over the second gate insulator film, is electrically separated from the floating gate by the second gate insulator film, and is electrically separated from the selector gate by the second gate insulator film and the first insulator film;
• the memory cells being arranged in a matrix form along a first direction of the main face of the semiconductor substrate and along a second direction perpendicular to the first direction;
• wherein (the) control gates of the memory cells arranged in each row along the first direction are connected to each other to constitute a word line;
• and
• wherein (the) selector gates of the memory cells arranged in each column along the second direction are connected to each other.