The fluorinated amorphous carbon thin films (a-C:F) were deposited by PECVD(plasma enhanced chemical vapor deposition). The precursors were C₄F_(8) which had a similar ratio of target film`s carbon to fluorine ratio, and Si₂H_(6)/He for capturing excessive fluorine ion. We varied deposition condition of temperature and working pressure to survey the effect of each changes. We measured dielectric constant, composition, and etc. At low temperature the film adhesion to substrate was very poor although the growth rate was very high, the growth rate was very low at high temperature. The EDS(energy dispersive spectroscopy) result showed carbon and fluorine peak for films and Si peak for substrate. There was no oxygen peak.