α-silicon carbide ceramics with different nitrogen content were fabricated by changing the post-HIP nitrogen gas pressure. Resultant silicon carbide ceramics were all n-type semiconductors in which doped nitrogen played a role of donor. With the doping pressure up to 150MPa, incorporated nitrogen were dissolved into silicon carbide. Lattice parameter, carrier concentration and piezoresistance coefficient changed in accordance with the solution content. Over 150MPa, nitrogen incorporation continued to increase while nitrogen solution was saturated.