PURPOSE: To reduce any stepped portion between adjacent word lines by providing the process of leaving behind a photoresist pattern on an interlayer film buried in a space between the adjacent line, and of removing the interlayer film of an area where no photoresist pattern existent to form a side wall film.

CONSTITUTION: There are introduced the processes of forming a word line 23 on a device isolation area of a semiconductor substrate 21, thereafter forming an interlayer film 25b over the entire surface of the substrate, and leaving behind a photoresist pattern between the work lines 23 by photolithography, and of etching the interlayer film 25b to form a side wall 25a on the side wall of the word line 23 and thereafter removing the photoresist 25a, Consequently, the side wall 25a is left behind on the side wall of the work line 23 where no photoresist pattern exists upon etching of the semiconductor substrate 21, and the interlayer film 25b is buried, without being removed, in a space between the adjacent work lines 23 where the photoresist pattern exists. Hereby, there can greatly be reduced any stepped portion between the adjacent word lines 23.