As a support of catalytic Co nanoparticles used for the growth of high-density single-walled carbon nanotubes (SWCNTs), conductive Co silicide films are superior to insulating SiO₂ films. A Co silicide films is formed through reaction between a Co thin film and the underlying Si wafer. During this process, however, a TiN cap film must be formed to prevent the Co thin film from forming Co nanoparticles and must be etched after the formation of the silicide film, which makes the formation process complicated. In this study, we optimized the thickness of the Co film and formed a silicide film without using a TiN cap film to simplify the formation process. As a result, the formation of the Co nanoparticles was greatly suppressed during the formation of a silicide film. Using the Co silicide film obtained after the formation process at 650^oC for 10 min as the support of catalytic Co nanoparticles, vertically aligned CNTs film with a thickness of 5.3 μm were obtained by hot-filament chemical vapor deposition (CVD) with ethanol steam at 450^oC for 30 min. This thickness is approximately 1.8-fold that previously reported.