The surface reaction of CF2 radicals on Si and fluorocarbon films was investigated in electron cyclotron resonance (ECR) Ar and H-2/Ar downstream plasmas employing CF2 radical injection technique. The effects of Ar+ ions, Ar* metastable species and radiation from plasmas on the fluorocarbon film formation were evaluated in ECR Ar downstream plasma with CF2 radical injection. As a result, CF2 radicals with assistance of Ar+ ion bombardment were found to play an important role in the fluorocarbon film formation. The adsorptive reactions of CF2 radicals on the fluorocarbon film surface with and without Ar and H-2/Ar plasma exposures were successfully investigated by in situ Fourier transform infrared reflection absorption spectroscopy and in situ x-ray photoelectron spectroscopy. It was found that the formation of fluorocarbon film in the plasma proceeded through the adsorptive reaction of CF2 radicals at a high probability on the active sites formed by the bombardment of Ar+ ions on the fluorocarbon film surface.