We studied the hydrogen plasma etching mechanism on (001) diamond surfaces as a parameter of misorientation angle (theta(off)). After hydrogen plasma etching, for theta(off) < 1.5 degrees, atomically flat surfaces were observed by atomic force microscopy, while for theta(off) > 1.5 degrees, rough surfaces with high etch pit density and large (200 nm) periodic pattern due to mechanical polishing were observed on diamond substrates. In addition, mean roughness (R-a) increased with the increase in theta(off). A simple model is presented taking into account anisotropic etching depending on theta(off). Simulated results based on the model well explain the experimental results. Based on these results, we discuss the effect of hydrogen plasma etching on the growth of atomically flat homoepitaxial chemical vapor deposition diamond film at low CH4/H-2 ratio with low theta(off). (c) 2006 Elsevier B.V. All rights reserved.