The authors investigated an aluminum oxynitride buffer layer for PrXOY/Si metal-insulator-semiconductor stacks. The buffer layer limits unintentional interfacial layer formations and improves the electrical parameters as determined by combined electrical and spectroscopic characterization methods. These benefits are attributed to an interaction of the oxygen of the buffer layer with the PrXOY. As essential parameters for the improved performance of the buffer layer the authors find an O:N ratio of 1 and a thickness of 1 nm. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3025905]