A method of manufacturing a DRAM capacitor is described. A silicon substrate structure includes an oxide layer over a substrate and a polysilicon layer over the oxide layer. The polysilicon layer also includes a plug that penetrates the oxide layer. A patterned photoresist layer is next formed over the polysilicon layer. Spacers having a low etching rate are formed on the sidewalls of the photoresist layer by carrying out a chemical reaction next to the sidewall of the photoresist layer. A dry etching operation is carried out to etch the unreacted photoresist layer and the polysilicon layer exposed by the openings in the photoresist layer. Using the spacers as an etching mask, a portion of the polysilicon layer under the photoresist layer is removed by continuing the dry etching operation. Lastly, the spacers are removed to form a crown-shaped capacitor.