Abstract: The present disclosure provides a fabrication method for forming a conductive plug structure, including: providing a semiconductor substrate; forming a contact hole in the semiconductor substrate; forming an insulating layer on the semiconductor substrate and a bottom and sidewalls of the contact hole; and forming a metal conductive layer on the insulating layer to fill up the contact hole, the metal conductive layer including two or more stacking metal conductive unit layers, each metal conductive unit layer having a metal nucleation layer and a metal bulk layer on the metal nucleation layer.