An evaluation of the effect of nitridation temperature on interface layer (IL) quality of Hf-silicate gate dielectric prepared by the atomic layer deposition method has been reported. An increase in IL density and IL roughness was observed by x-ray reflectivity as the nitridation temperature was increased. X-ray photoelectron spectroscopy showed preferential interface reaction at the dielectric-Si interface at higher temperatures. The progressive increase in IL roughness finally led to degradation of the breakdown voltage, a shift in flat band voltage (similar to 0.54 V), and deterioration of electron channel mobility by similar to 20% in samples nitrided at 850 degrees C. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3043536]