The a-C∶H(N) films was deposited from the mixture of C2H2 and N2 by rf-dc plasma enhanced chemical vapor deposition. The influence of N2 percentage in the mixture on the composition and structure of a-C∶H(N) films was studied by XPS. As the N2 percentage in the feed gas was increased from 0% to 75%, up to 9.09% N was incorporated in the film. The results of analysing C1s and N1s core level indicated that a-C∶H(N) films are consisted of stoichiometry C3N4 phase and CHx matrix which is identified as predominantly sp2 bonded structure. The N/C ratio of C3N4 phase is near 4/3. The N atoms incorporated in the films is useful to increase the content of C3N4 phase and sp3/sp2 ratio.