. Crystallographically specific pyramidal planes in 4H-SiC could be naturally formed at mesa sidewalls by a thermal etching at 900oC in a chlorine (Cl2) based ambience. The mesa structures have been fabricated on the 4H-SiC C-face with 0-45o off-angle toward [11-20]. The etched surface was rather smooth, and bunched step structures on the specific pyramidal planes were not observed with atomic force and scanning electron microscopes. The formation mechanisms of the specific pyramidal planes at mesa sidewalls are discussed on the basis of these experimental results.