The a-C:F films were deposited on a p-type Si(100) substrate using an inductively coupled plasma chemical vapor deposition (ICPCVD) system with a mixture of CF4 and CH4 gases. A CF4 plasma treatment with various treatment times was carried out in situ for an as-deposited a-C:F film. The CF4 plasma treatment changed the bonding configuration of the a-C:F film from the fluorine-rich functional groups of C-Fx bonds to the carbon-rich functional groups of -CF-C-CFx bonds when the plasma treatment time was up to 30 s. However when the plasma treatment time was increased, the bonding structure induced a rearrangement of the chemical bonds forming carbon-rich functional groups in which C-F, C-F2 and C-F3 bonds decreased and the peak intensity of the C-C bond increased. The lowest dielectric constant of the a-C:F film was about 2.3 for 30 s plasma treatment time and the electronic susceptibility and the surface charge per electric field were found to be 1.09×10?11 C/V·m and 0.99×10?18 C·m/V, respectively.