Ultra thin HfO2/Al2O3/HfO2 triple-layer gate dielectrics for advanced MIS capacitors have been characterized electrically. The triple-layer gate stacks after post-metal annealing (PMA) at various temperatures have been studied. Experimental results including leakage current, C-V characteristics, and TDDB are presented in this paper. It has been found that the addition of Al2O3 into HfO2 increases the crystallization temperature of the gate dielectric, and thus reduces the leakage current. The best overall characteristics were obtained by applying PMA at 600 °C.