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Nickel-based Schottky contacts to n-6H-SiC, subjected to various heat treatments, have been studied by the capacitancevoltage technique, X-ray diffractometry and AES sputter depth profile methods. Substrate heating during nickel deposition and additional annealing of Schottky contacts after deposition of metal film lead to differences in structure and composition between contact layers formed on Si- and C-faces. As a result a distinction in surface barrier heights in Schottky diodes formed on the C-and Si-faces has been observed. At annealing temperatures higher than 400–600 °C formation of nickel silicides in the contact layer is starting. Low-resistance (< 10⁻⁴ Ω cm²) ohmic contacts to the 6H-SiC polar faces were fabricated after annealing Ni-n-6H-SiC Schottky diodes at 1000 °C.