A novel technology "PH3 plasma doping process" is used to improve the reduction of C-min/C-max 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 C-min/C-max ratio. In PH3 plasma doping process, phosphorus diffuses in Si by interacting with vacancies, Using the storage electrode with MSG-Si doped in PH3 plasma, the capacitor has 96% of C-min/C-max ratio and no degradation of capacitor properties caused by excess phosphorus incorporation into dielectrics.