In this paper the interface trap densities (D-it) of 4H and 6H-SiC MOSFETs in the subthreshold region have been studied. Interface trap densities in this region were extracted as a function of trap energy (ET) from the transfer characteristics. We show these interface trap densities increase exponentially approaching the onset of strong inversion for both polytypes, and D-it(E-T) is higher in 4H than in 6H through the subthreshold region. These results are consistent with previous reports [1-6]. (C) 2002 Elsevier Science Ltd. All rights reserved.