Patent ID: 6919246

Claim:
A method for fabricating a semiconductor device, which comprises the steps of: providing a semiconductor substrate having a first conductive type well formed therein; forming a first trench in the semiconductor substrate including the first conductive type well, wherein the step of forming the first trench preferably comprises the sub-steps of: forming a pad oxide film and a first nitride film on the surface of the first conductive well; successively patterning the first nitride film, the pad oxide film and the first conductive well so as to form an initial trench; forming sacrificial oxide films on both sidewalls of the initial trench; forming a second nitride film in the initial trench at a portion between the sacrificial oxide films; removing the sacrificial oxide films; and successively removing a portion of the first conductive type well and a portion of the semiconductor substrate below the first conductive type well, using the second and first nitride films as mask, thereby forming the first trench; forming a plate electrode on the surface of the first trench; forming a capacitor insulating film on the surface of the plate electrode; forming a storage node electrode in the first trench including the capacitor insulating film; forming a first insulating film for planarization over the storage node electrode; forming a second trench in the portion of the first conductive type well, which does not correspond to the first trench; forming a gate insulating film on the surface of the second trench; forming a gate electrode on the portion of the gate insulating film, which is located on the sidewall of the second trench; and forming drain and source regions on the upper and lower portions of the first conductive type well, respectively, which correspond to the sidewall of the second trench.