Dielectric barrier discharge (DBD) plasma was used to modify polyethylene terephthalate (PET) films with gradient roughness and homogenous surface chemistry. Based on asymmetric electrode arrangement, the spatial distribution of the plasma on the films surface was non-uniform, leading to the formation of typical three discharge regions (central zone, boundary zone and diffuse zone). The experimental results showed that the plasma induced significant morphological and chemical changes onto the surfaces. Furthermore, a gradient surface roughness from central zone to diffuse zone was formed, while surface chemistry was relatively homogenous in these regions, which can be explained by theoretical plasma-etching mechanism. (C) 2017 Elsevier B.V. All rights reserved.