Method of fabricating semiconductor device having a trenched cell capacitor

A method for fabricating a semiconductor device, adapted for a MOS type DRAM having a grooved cell capacitor portion formed in a main surface of a semiconductor substrate, comprising the steps of:

• forming a first layer of the same conductivity type as that of the semiconductor substrate on a selected portion of the semiconductor substrate with an oxidization-resistant first insulating film as a first mask, and performing thermal oxidization to form a field oxidized film;
• removing the first insulating film;
• forming a second mask on an entire surface of the semiconductor substrate;
• forming an opening in the second mask at the portion which is in a close proximity to the field oxidized film;
• etching the semiconductor substrate to form a groove;
• performing oblique rotational ion injection into a portion of the groove other than a side wall portion of the groove adjacent the first layer with the second mask as a peak-shaped mask, forming only in a selected region inside the groove a second layer of the same conductivity type as that of the semiconductor substrate;
• removing the second mask;
• forming a third layer of an opposite conductivity type to that of the semiconductor substrate at least on the entire side wall of the groove;
• and
• forming a dielectric film and a conductive electrode in the groove.

A method for fabricating a semiconductor device, adapted for a MOS type DRAM having a grooved cell capacitor portion formed in a main surface of a semiconductor substrate, comprising the steps of:

• forming a first layer of the same conductivity type as that of the semiconductor substrate on a selected portion of the semiconductor substrate with an oxidization-resistant first insulating film as a mask, and performing thermal oxidization to form a field oxidized film;
• removing the first insulating film;
• forming on an entire surface of the semiconductor substrate a second film durable against groove etching and functioning as a mask against ion injection;
• forming an opening in the second film at the portion which is in a close proximity to the field oxidized film;
• etching the semiconductor substrate to form a groove;
• performing oblique rotational ion injection into a portion of the groove other than a side wall portion of the groove adjacent the first layer with the second film as a peak-shaped mask, forming only in a selected region inside the groove a second layer of the same conductivity type as that of the semiconductor substrate;
• removing the second film;
• forming a third layer of an opposite conductivity type to that of the semiconductor substrate at least on the entire side wall of the groove;
• and
• forming a dielectric film and a conductive electrode in the groove.