Fluorinated amorphous carbon (a-C:F) thin films were deposited by inductively coupled plasma enhanced chemical vapor deposition and annealed with increasing annealing temperature (100, 200: 300, 400 degreesC). The evolution of composition, dielectric constant, and bonding configuration were investigated during the thermal annealing process. As the annealing temperature increased, the dielectric constant varied from 2.4 to 3.6; the atomic ratio of F varied from 25 to 10%, and that of C varied from 75 to 85%; in the C-F-x bonding configurations, the C-F bondings decrease and the C-F-2 and C-F-3 bondings are almost constant. Thus, the C-F-2 and C-F-3 bonding configurations are thermally more stable than the C-F bonding configuration. The structure of the film changes to a crosslinked structure by an increase in the C-C bonding and a decrease in the C-F bonding.