Method for fabricating nonvolatile memory device

A method for fabricating a nonvolatile memory device, the method comprising:

• 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 which is not covered by the isolation layer;
• recessing a portion of the exposed isolation layer using the spacers as an etch barrier layer to form a wing spacer;
• removing the spacers;
• performing a primary cleaning process on the resulting substrate, where the spacers are removed, using a mixed solution of sulphuric acid (H2SO4) and hydrogen peroxide (H2O2) and a mixed solution of ammonium hydroxide (NH4OH), H2O2, and H2O;
• and
• performing a secondary cleaning process on the resulting structure, where the primary cleaning process is completed, using a mixed solution of a hydrogen fluoride (HF) solution and a deionized water and a mixed solution of NH4OH, H2O2, and H2O.