Al/AlN/n-type 6H-SiC (0001) MIS structures were prepared by AlN layers on vicinal 6H-SiC(0001) substrates with reactive RF magnetron sputtering method. The AlN films were annealed at $900^{circ}C$, $N_2$ atmosphere lot 1 minutes showed the best result. With XRD analysis, AlN(0002) peak was clearly found. The typical dielectric constant value of the AlN film in the MIS capacitors was obtained as 8.4 from photo C-V. Also, the gate leakage current density of the MlS capacitor was $10^{-10};A/cm^2$ order within the electric field of 1.8 MV/cm. Finally, the amount of interface trap densities, $D_{it}$, was evaluated as $5.3 imes10^{10};eV^{-1}cm^{-2}$ at (Ec-0.85) eV.