Fluorinated amorphous carbon films (a-C:F) were prepared at different temperaturesusing a microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactorwith CHF3 and C2H2 as source gases. Films were annealed at 500 ℃ in vacuum ambience inorder to investigate the relationship of their thermal stability, optical and electrical propertieswith deposition temperature. Results indicate that the films deposited at high temperature havea less CFx bonding and a more cross-linking structure thus a better thermal stability. They alsohave a lower bandgap, higher dielectric constant and higher leakage current.