PURPOSE: To lessen a junction capacity of a source and a drain and thereby to attain a high speed and low consumption of a current by forming a side spacer on the side wall parts of a CVD oxide film and a nitride film by etching them, and by forming a channel stopper by implantation.

CONSTITUTION: A first oxide film 2 being as thin as 150 to 2000 angstrom is formed on the surface of an N substrate 1 and a nitride film 3 of 500 to 20000 angstrom and a second oxide film 4 of 2000 to 5000 angstrom are formed thereon sequentially. Next, the films 3 and 4 are etched and then boron is implanted, in the amount of implantation of 2×1012 to 8×1012ion/cm2, in a region of the N substrate 1 wherein an LOCOS oxide film is to be formed, so as to form a P-type layer 5 of low concentration. Then, an oxide film is formed on the whole surface and overall etch-back is conducted, so as to form a side spacer 6 on the side wall parts of the films 3 and 4. After phosphorus is implanted as a channel stopper in the region wherein the LOCOS is to be formed, the oxide films 2 and 4 and the side spacer 6 are removed and thereby the LOCOS oxide film 8 is formed.