PURPOSE: To form uniform 2nd polycrystalline silicon film and eliminate the remnants of the 2nd polycrystalline silicon film by a method wherein side wall are formed on the edges of 1st polycrystalline silicon film and, after the 2nd polycrystalline silicon film is formed over the whole surface, a control gate and a word line are formed by anisotropic etching.

CONSTITUTION: A field oxide film 2 and a gate oxide film 3 are formed on a substrate 1 and 1st polycrystalline silicon film 4 is formed. Then a CVD oxide film 7 is formed over the whole surface so as to cover the 1st polycrystalline silicon film 4 and anisotropic etching is applied to the whole surface to form side wall films 6 whose top surfaces are inclined on the edges of the 1st polycrystalline silicon film 4. All the CVD oxide film 7 is removed by etching and a silicon oxide film 8 is formed on the upper surface of the polycrystalline silicon film 4. Then 2nd polycrystalline silicon film 9 which is to be a control gate and a word line is formed over the whole surface of the 1st polycrystalline silicon film 4 with the silicon oxide film 8 between and patterned to form the required control gate and word line.