A method for manufacturing a semiconductor device comprising: providing a substrate, wherein an amorphous silicon layer is formed on the substrate; forming an etching auxiliary layer on the amorphous silicon layer, wherein the upper surface of the etching auxiliary layer is flat, and the etching auxiliary layer is made of a single material; and etching the amorphous silicon layer and the etching auxiliary layer to obtain an amorphous silicon layer with a target thickness, wherein the upper surface of the etched amorphous silicon layer is flat.