Fabrication method and structure of semiconductor non-volatile memory device

Abstract

A non-volatile semiconductor memory device with good write/erase characteristics is provided. A selection gate is formed on a p-type well of a semiconductor substrate via a gate insulator, and a memory gate is formed on the p-type well via a laminated film composed of a silicon oxide film, a silicon nitride film, and a silicon oxide film. The memory gate is adjacent to the selection gate via the laminated film. In the regions on both sides of the selection gate and the memory gate in the p-type well, n-type impurity diffusion layers serving as the source and drain are formed. The region controlled by the selection gate and the region controlled by the memory gate located in the channel region between said impurity diffusion layers have the different charge densities of the impurity from each other.

1 . A semiconductor device comprising memory cells, each memory cell including:
 a semiconductor substrate;   a first gate insulating film formed over the semiconductor substrate;   a first gate electrode formed over the first gate insulating film;   a second gate insulating film including an insulating film for charge storage formed over the semiconductor substrate and over a side wall of the first gate electrode; and   a second gate electrode formed over the second gate insulating film, adjacent with the first gate electrode through the second gate insulating film,   wherein the second gate electrode is formed of a first polycrystalline silicon film formed over the second gate insulating film and a second polycrystalline silicon film formed over the first polycrystalline silicon film.   
     
     
         2 . A semiconductor device comprising memory cells according to  claim 1 ,
 wherein the first polycrystalline silicon film has a first portion extending along a surface of the semiconductor substrate and a second portion extending along a direction perpendicular to the surface of the semiconductor substrate.   
     
     
         3 . A semiconductor device comprising memory cells according to  claim 1 ,
 wherein the second electrode is in the form of a side wall.   
     
     
         4 . A semiconductor device comprising memory cells according to  claim 1 ,
 wherein the second gate insulating film includes:   a first silicon oxide film formed over the semiconductor substrate and over the side wall of the first gate electrode;   a silicon nitride film formed over the first silicon oxide film; and   a second silicon oxide film formed over the silicon nitride film,   wherein the silicon nitride film is the insulating film for charge storage.