In contrast to narrow bandgap semiconductors such as silicon, common doping elements in SiC have activation energies larger than the thermal energy k(B)T even at room temperature. Inequivalent a-SiC sites, one with cubic (k) surrounding and the other with hexagonal (h) surrounding are expected to cause site-dependent impurity levels. Therefore, an appropriate incomplete ionization model which accounts for lattice site-dependent ionization level of impurities in a-SiC has been developed and implemented in the general-purpose device simulator MINIMOS-NT.