PURPOSE: To manufacture a semiconductor memory easily by etching Si by a method wherein, after forming multiple island regions in a semiconductor substrate, sidewalls of prospective MOS capacitor forming region of respective regions are exposed by etching island regions.

CONSTITUTION: An oxide film 2 is formed on a p-type Si substrate 1; a photoresist 3 is pattern-formed in an island region to etch the film 2; first a field groove 4 is formed. Later, a p-type layer 5 for isolating element is formed on the bottom of this groove 4. Second, the resist 3 and the film 2 are removed to bury another oxide film 6 flatly in the groove 4. Third, another groove 8 is formed to expose the sidewalls and bottoms in a prospective sidewall capaci tor forming region. Fourth, an n-type layer 10 to be a substrate side electrode of MOS capacitor is formed. Successively, a capacitor part insulating film is formed to form a capacitor electrode 12. Through these procedures, a semicon ductor memory can be manufactured easily by Si etching process only without etching-back an in sulating film with a cell buried therein.