To date, many studies have been carried out to investigate the use of semiconductive diamonds in industrial applications. In these studies, it has been necessary to deposit high-quality crystalline diamond thin films on large-area substrates. Hot-filament chemical vapor deposition (HFCVD) has been a useful method for generating these thin films. While large-area silicon (Si) substrates are easily obtainable and inexpensive and Si is a suitable material for the deposition of diamond thin films, because of the large mismatch of the lattice constants of Si and diamond, it is usually difficult to grow epitaxial diamond films on Si substrates. Therefore, insertion of a buffer layer comprised of a material with a lattice constant between those of Si and diamond is required. Silicon carbide (SiC), which is readily obtained by carbonization of the Si surface, is a candidate material for such a buffer layer. Therefore, in this study, a char layer was formed on a Si surface using HFCVD equipment and analyzed from various perspectives.