A plasma-enhanced copolymerization technology has been developed in which organic precursors are designed and synthesized to form polymerized films with low dielectric constants. In order to lower the dielectric constant, a tricyclodecane (TCD) group is introduced as an organic precursor molecule because TCD is a large aliphatic hydrocarbon group, which contributes to lowering the film density. The TCD precursors are liquid at room temperature and they have a sufficient saturated vapor pressure to be applicable to the vapor phase deposition. The optimized dielectric constant of the TCD polymer was less than 2.5. A solid C-13 nuclear magnetic resonance spectrum showed that the TCD moiety in the precursor was included in the polymer without changing the structure. The effect of the substrate temperature on the film structure was studied by analyzing Raman spectra. It was revealed that the dielectric constant was associated with sp(2) carbon content in the TCD-based polymer films. (c) 2007 The Electrochemical Society.