Abstract: SiO_x/a-C: F/SiO_x multiple-layer films were prepared by microwave electron cyclotron resonance chemical vapor deposition （ECR-CVD） method using 20% SiH₄ in Ar, O₂, CHF₃ and CH₄ as precursor. The Fourier transform infrared absorption spectra show that there are many C-F, C = C, Si-O bondings in the multiple-layer films. Meanwhile, because of the "absorption effect" of the vacuum chamber, a small quantity of Si-C and Si-F bondings exist in the multiple-layer films, which is verified by deep layer analytic result from x -ray photoelectron spectroscopy. Furthermore, the effect of annealing indicates that the FTIR structure of the films does not change obviously after 400℃ annealing, and the dielectric constant increases only 8%. In a word, SiO_x/a-C: F/SiO_x multiple-layer films prepared by ECR-CVD may be one of the candidate materials for interlayer dielectrics in ULSI.