To improve electrical characteristics of high-k gate dielectrics, post-deposition annealing (PDA) was performed in high-pressure (10 atm) pure hydrogen ambient. High-pressure PDA samples show excellent electrical characteristics such as low fixed charge density, and reduced interface state density confirmed by capacitance-voltage analysis and conductance technique, respectively. They also showed no frequency dependency and a hysteresis of 2.9 mV. The leakage current decreases remarkably from 0.23 to 2.44 x 10(-7) Ampere/cm(2) at the gate voltage of 1 V below V-FB. The excellent electrical characteristics of high-pressure hydrogen annealed sample can be explained by enhanced hydrogen passivation of defects in high-k dielectric. (c) 2006 The Electrochemical Society.