To properly and easily implant channel stopper ions in all the region of the interior, which is located under a field oxide film, of a substrate by a method wherein the field oxide film is formed on the region, of the substrate which is exposed through an oxide film growth inhibition film the edge parts of the inhibition film are removed, and the edge of the inhibition film is made to expose.
A semiconductor substrate 10, which is partially covered with a silicon nitride film 12 of an oxide film growth inhibition film, is heat-treated to grow integrally a pad oxide film 11 and a field oxide film 13. Then, the edge parts 12a of the film 12 are partially removed using a silicon oxide film 15 as an etching mask. Then, channel stopper ions are preparatorily implanted in the edge 13a of the film 13 being exposed through the film 12. After this, the films 15, 12 and 11 are removed in order by etching, and channel stopper ions are implanted in the substrate 10 all over the surface through the surface of the substrate 10.
