In this article, we present a new method for the synthesis of amorphous nitrogenated carbon films using an alternate CH4 plasma deposition/subsequent N-2 plasma treatment, so-called alternate plasma deposition (APD), in a dual electron cyclotron resonance (ECR)-rf plasma. The nitrogen to carbon ratio in the film surface deposited by this method, estimated by x-ray photoelectron spectroscopy (XPS), is considerably higher, by about a factor of 2, than that obtained in the film deposited from a conventional CH4/N-2 plasma. From infrared spectroscopy it is shown that the APD film has the more enhanced disordered phase, which is accompanied by an increase of the amount of sp(2) hybridized carbon-nitrogen bonds, as shown by XPS spectra.