Patent ID: 7795084

Claim:
A method for fabricating a semiconductor device comprising: (a) forming a buffer oxide layer and a buffer nitride layer on the top surface of a semiconductor substrate; (b) forming a photoresist pattern on the pad nitride layer and forming a trench by etching the buffer nitride layer, the buffer oxide layer, and the semiconductor substrate by a predetermined etch using the photoresist pattern as a mask; (c) forming sidewall floating gates on the lateral faces of the trench; (d) depositing polysilicon on the semiconductor substrate including filling the trench; (e) patterning the polysilicon to form a gate electrode; (f) removing the buffer nitride layer after forming the gate electrode, and forming a poly oxide layer on the exposed part of the polysilicon of the gate electrode; (g) forming source/drain regions by implanting impurities into the semiconductor substrate, wherein the source region is elevated to the same level as the drain region; (h) injecting electric charges into the sidewall floating gates; and (i) forming spacers on the lateral faces of the sidewall floating gates and the gate electrode.