High-gas-barrier layer deposition technology is very important for fabricating film-based organic light-emitting diode lighting. In this study, we fabricated high-quality water vapor barrier films using hexamethyldisiloxane, TG-41, or both as precursors. The barrier layer was deposited on polyethylene naphthalate or polyethylene terephthalate using roll-to-roll plasma-enhanced chemical vapor deposition. The barrier film fabricated using TG-41 as the precursor had high transparency. It is found that the stacking structure of layers with compositions close to SiOx and carbon components remaining in SiOx is important for depositing a barrier layer with good water vapor barrier properties using a roll-to-roll process.