A method for fabricating a nonvolatile memory device includes forming a tunneling insulation layer and a conductive layer for a floating gate over a substrate, partially etching the conductive layer, the tunneling insulation layer, and the substrate to form a trench, forming an isolation layer filling a portion of the trench, forming spacers on both sidewalls of the conductive layer not covered by the isolation layer, recessing a portion of the exposed isolation layer using the spacers as an etch barrier layer to form wing spacers, removing the spacers, performing a primary cleaning process on the resulting substrate using a mixed solution of H2SO4 and H2O2 and a mixed solution of NH4OH, H2O2, and H2O, and performing a secondary cleaning process on the resulting structure using a mixed solution of a HF solution and a deionized water and a mixed solution of NH4OH, H2O2, and H2O.