RF power and DC bias have been simultaneously applied to the target in a conventional magnetron sputtering system in order to control the growth kinetics of Ta films. Lowering the target DC bias V-T down to -100 V results in a significant decrease in the Ar content in the Ta film, which is reduced to below the detection limit Of electron prove microanalysis (EPMA, less than 0.05 wt.%) for V-T = -100 V. It is shown that the resistivity and the crystalline structure of the Ta thin overlayer on every thin film of Mo depend on the thickness of Mo films. The resistivity for Ta films with alpha-Ta phase at the very thin Mo films (about I nm) was obtained at similar to 20 mu Omega cm, whose value was one seventh of that for the Ta films without the underlayer Mo thin films.