Graphite film was used as a protective and selective mask for realizing diffusion of boron in SiC. Secondary ion mass spectroscopy was employed to identify the diffusion profile in SiC. No significant difference between diffusion profiles in 4H-SiC and 6H-SiC was found. Planar p-n diodes with local p-type emitter regions were fabricated in 4H-SiC and 6H-SiC based on this process. The current density versus voltage (J-V) curves of the formed diodes exhibited good rectification characteristics. The 4H-SiC p-n diodes had much lower forward voltage drops and much less temperature dependence in comparison with 6H-SiC p-n diodes.