Comments are made on a recent article by Kim, Chang, and Kim [J. Vac. Sci. Technol. A 21, 426 (2003)], which describes the preparation and the x-ray photoemission spectroscopy study of the etching effects produced by Ar-based plasmas of different composition on the surface chemistry of a CeO2 film grown on Si. We discuss some chemical interactions taking place between Ce, Si, and the ambient humidity during the early stages of film deposition, and demonstrate that the many-body effects involved in Ce3d spectra provide a key for better understanding of the etching mechanisms exerted by the plasma treatments.