Pulsed metalorganic chemical vapor deposition (MOCVD) of conformal copper seed layers, for the electrodeposition Cu films, has been achieved by an alternating supply of a Cu(I) source and H2 reactant at the deposition temperatures of 50 - 100°C. The Cu thickness increased proportionally to the number of cycle, and the growth rate was in the range of 3.5 to 8.2 A /cycle, showing the ability to control the nano-scale thickness. As-deposited films show highly smooth surfaces even for more than 100nm. In addition, about a 90% step coverage was obtained inside trenches, with an aspect ratio greater than 30:1. H2, introduced as a reactant gas, can play an active role in achieving highly conformal coatings, with increased grain sizes.