A high-temperature annealing method was developed to obtain an atomically flat surface for Si(1 00). Maintaining a smooth reconstructed surface is very important for restricting accidental oxidation during the unloading process (i.e., reflow oxidation) after high-temperature annealing. We evaluated the thickness of the reflow oxidation layer and the surface structure obtained on a Si(1 0 0) wafer when we replaced the injected Ar gas with H(2) during the cooling process after high-temperature Ar annealing. A H-terminated Si(1 0 0) surface was formed by H(2) annealing during the cooling process, and this formation effectively suppressed reflow oxidation. However, the H(2) atmosphere also caused etching of the reconstructed Si(1 0 0) surface; nevertheless, atomic force microscopy (AFM) measurements revealed that the Si(1 0 0) surface roughness drastically decreased when subsequent roughness variation regarded as being caused by the oxidation occurred. The results suggest that our method is effective in restraining increases in surface roughness at the atomic level that are caused by oxidation. (c) 2010 Elsevier B.V. All rights reserved.