The present invention discloses a method for reducing the morphological difference between N-doped and undoped poly-silicon gates after etching, comprising the following sequential steps: depositing a hard mask layer on a substrate template having N-doped poly-silicon and undoped poly-silicon to form an N-doped poly-silicon hard mask layer and an undoped poly-silicon hard mask layer respectively, and etching the undoped poly-silicon hard mask layer to make a thickness difference between the N-doped poly-silicon hard mask layer and the undoped poly-silicon hard mask layer; depositing an anti-reflection layer, and etching according to a predetermined pattern until exposing the N-doped poly-silicon, wherein when the N-doped poly-silicon is exposed, the undoped poly-silicon is etched to a certain degree; and removing residuals on the surface of the above formed structure, and etching to form an N-doped poly-silicon gate and an undoped poly-silicon gate, respectively.
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