Numerical simulations of microscopic and macroscopic device properties of field effect transistors in 4H- and 6H-SiC are presented. The microscopic properties have been simulated using a full band (ab initio method) Monte Carlo simulation model and the macroscopic properties have been simulated using a drift-diffusion model with transport parameters obtained from the Monte Carlo simulations. Different models for the SiC/SiO2 interface in SiC MOSFETs have been evaluated and compared with experimental data. Finally, we present a comparison of simulated device performance for MOSFETs and MESFETs in 4- and 6H-SiC technologies. Both vertical (SIT) and lateral MESFET structures have been considered