Method for fabricating capacitor of semiconductor device

A method for fabricating a capacitor of a semiconductor device, comprising the steps of:

• forming an insulation layer having contact holes on an upper surface of a substrate;
• forming a plurality of plugs connected to the substrate by being filled into the contact holes;
• forming an isolation layer having holes exposing the plurality of the plugs on the insulation layer;
• forming a first amorphous silicon layer doped with an impurity in a predetermined first doping concentration suppressing dopants from locally agglomerating;
• forming an impurity undoped second amorphous silicon layer on the first amorphous silicon layer in an in-situ condition;
• forming a storage node by patterning the first amorphous silicon layer and the second amorphous silicon layer;
• forming silicon grains on a surface of the storage node;
• and
• doping the impurity to the storage node and the silicon grains until reaching a second predetermined concentration for providing conductivity required by the storage node.