Semiconductor device having contact electrode to semiconductor substrate

A semiconductor device comprising:

• a semiconductor substrate;
• an isolation region embedded in said semiconductor substrate, identified by an upper-face height having a substantially same height of a surface of said semiconductor substrate;
• an active region formed at the surface of and in said semiconductor substrate;
• a field insulator disposed on said isolation region, identified by a side face being continuous with a face extending an internal side face of said isolation region of an entire circumference of the surface of the semiconductor substrate;
• a cylindrical sidewall insulator contacting with the internal side face of said field insulator;
• and
• a contact electrode formed on said active region.

A method for fabricating a semiconductor device comprising:

• forming an etching mask on a semiconductor substrate;
• forming a trench in the semiconductor substrate;
• filling the trench with an isolation insulator so as to form an active region in the semiconductor substrate surrounded by the isolation insulator;
• planarizing an upper face of the isolation insulator and a surface of the semiconductor substrate;
• filling an opening of the etching mask with a field insulator so as to dispose the field insulator on the isolation insulator;
• forming an isolation-sidewall insulator at an inner side face of the field insulator;
• forming an interlevel insulating film having an etching rate larger than that of the isolation-sidewall insulator on an entire surface;
• forming an opening for exposing the active region in the interlevel insulating film;
• and
• forming a conductor in the opening and electrically connecting the conductor to the active region.