The atomic distortion and internal layer roughness in epitaxial 3C- and 4H-SiC thin films and bulk 6H-SiC are studied by means of short wavelength X-ray diffraction using a 0.71 Angstrom X-ray source from a molybdenum anode. Up to five order Bragg peaks along (100) were measured. Through the detailed theoretical calculation, the crystallographic structure factors were obtained. The electron density distributions along the surface normal were reconstructed via Fourier transform. Comparison with the ideal situation calculated from the atomic scattering factors was presented.