Nitrogen doped fluorinated amorphous carbon thin films for low dielectric constant interlayer dielectrics have been investigated. The films were deposited with a parallel‐plate plasma enhanced chemical vapor deposition. Source gases were CH4, CF4, and N2. The thermal stability of the films can be improved by the addition of N2. X‐ray photoelectron spectroscopy (XPS) measurement revealed that the C‐N bonds were formed in the films with the addition of N2. The dielectric constant of the films was increased from 2.1 to 2.4 at the nitrogen concentration of 10%. ©1996 American Institute of Physics.