A semiconductor device having a polymer layer and a method of fabricating the same is provided. A two-step plasma treatment for a surface of the polymer layer includes a first plasma process to roughen the surface of the polymer layer and loosen contaminants, and a second plasma process to make the polymer layer smoother or make the polymer layer less rough. An etch process may be used between the first plasma process and the second plasma process to remove the contaminants loosened by the first plasma process. In an embodiment, the polymer layer exhibits a surface roughness between about 1% and about 8% as measured by Atomic Force Microscopy (AFM) with the index of surface area difference percentage (SADP) and/or has surface contaminants of less than about 1% of Ti, less than about 1% of F, less than about 1.5% Sn, and less than about 0.4% of Pb.