A novel technology “PH3 plasma doping process” is used to improve the reduction of Cmin/Cmax ratio due to the depletion layer generation on the surface of storage electrode. The storage electrode with hemispherical-grained silicon (HSG–Si) made from amorphous silicon (a-Si) with low concentration of phosphorus has no bald defect but low Cmin/Cmax ratio. In PH3 plasma doping process, phosphorus diffuses in Si by interacting with vacancies. Using the storage electrode with HSG–Si doped in PH3 plasma, the capacitor has 96% of Cmin/Cmax ratio and no degradation of capacitor properties caused by excess phosphorus incorporation into dielectrics. © 1999 American Vacuum Society.