Methods for depositing film stacks by plasma enhanced chemical vapor deposition are described. In one example, a method for depositing a film stack on a substrate, wherein the film stack includes films of different compositions and the deposition is performed in a process station in-situ, is provided. The method includes, in a first plasma-activated film deposition phase, depositing a first layer of film having a first film composition on the substrate; in a second plasma-activated deposition phase, depositing a second layer of film having a second film composition on the first layer of film; and sustaining the plasma while transitioning a composition of the plasma from the first plasma-activated film deposition phase to the second plasma-activated film deposition phase.