SEMICONDUCTOR STORAGE DEVICE AND ITS MANUFACTURING METHOD

摘要

Impurity diffusion layer to serve as bit lines are formed in the surface region of a semiconductor substrate. Buried insulating films are formed over the impurity diffusion layer. A gate electrode of a memory element has first polycrystalline silicon films that are formed on a trap film and between buried insulating films and have a height approximately equal to that of the buried insulating films and second polycrystalline silicon films over the buried insulating films and first polycrystalline silicon films and adapted to electrically interconnect the first polycrystalline silicon films.