We have successfully synthesized homoepitaxial diamond films with atomically flat surface by the microwave plasma chemical vapor deposition (CVD) using an extremely low CH4/H-2 ratio of CH4/H-2 gas less than 0.15% CH4/H-2 ratio and Ib(0 0 1) substrates with low misorientation angle (theta(off)) less than 1.5degrees. It was found that surface morphologies of the films strongly depend on a growth condition of CH4/H-2 ratio and theta(off) of the substrate and was suggested that the hydrogen etching and the theta(off) played an important role for the epitaxial diamond film growth with an atomically flat surface, On the other hand, from the cathodoluminescence spectra and Schottky junction properties of these diamond films with atomically Rat surface, it has been clarified that these films have actually a high potentiality for electronic devices. (C) 2002 Elsevier Science B.V. All rights reserved.