For the practical application of diamond semiconductor devices, the manufacture of planar-type devices is important. Homoepitaxial growth of diamonds would be a useful technique for making semiconducting diamond films. Homo-epitaxial growth of diamonds is achieved by microwave plasma CVD. The properties of epitaxial diamond films depend on the deposition condition and the substrate orientation. Boron doping was easily carried out by this method and boron doped films were determined to be ptype semiconductors. Properties of boron doped epitaxial films were found to be similar to those of natural IIb diamond. The Schottky junction on boron doped epitaxial films was obtained by the deposition of tungsten and aluminum. The Schottky properties of this combination were affected by the surface roughness of the epitaxial films. A field effect transistor and a light emitting device were successfully fabricated using boron doped epitaxial films and Schottky junctions.