Plasma enhanced chemical vapor deposition of the Cu films on Si substrate was investigated in which 30 Angstrom Cu-seed layer on the substrate was formed by partially ionized beam prior to deposition. In order to elucidate the difference in growth mechanism of Cu film between on Cu-seed layer and on bare Si, the initial stage of Cu-seed layer grown by partially ionized beam was studied by transmission electron microscopy and different nucleation formation processes from conventional method was shown. A high deposition rate and an improved adhesion strength were achieved when thick Cu film on the Cu seeded Si substrate was deposited by plasma enhanced chemical vapor deposition.