The atomically flat surface is obtained by the ultra-pure argon ambient at relatively low temperature less than 900°C, and it can be maintained by using the N 2 ambient with light shielding cleaning and the radical oxidation. The crystal originated particles (COPs) on the wafer is also decreased by the argon annealing at 900°C. The charge to break down (Q bd of the radical gate oxide on the atomically flat silicon surface was evaluated. For the early period in the annealing treatment, the initial failure of Q bd which is often observed on the conventional flat surface disappears, however, the intrinsic lifetime is still the same as the conventional one. And then, the intrinsic lifetime is improved by completing atomically flat treatment. After roughening the atomically flat silicon surface, the Q bd characteristics of gate oxides on the Cz wafer is the same as that on the epitaxial wafer which does not have COP.