In this paper we report our research on DC and S parameter simulations and DC and RF characteristics experimental results of 4H-SiC MESFETs on a high purity semi-insulating substrate. 4H-SiC MESFETs were fabricated using home-grown epi structures. We designed our own devices process to fabricate n-channel 4H-SiC MESFETs with 200 mu m gate periphery. At a frequency of 2 GHz and at 79 V drain voltage, the maximum output power density CW is measured to be 7.8 W/mm, with a gain of 11.9 dB, and power-added efficiency 40%. The cut-off frequency (f(T)) and the maximum oscillation frequency (f(max)) is 8.7 GHz and 25.5 GHz, respectively. The simulation result of f(T) and f(max) is 11.4 GHz and 38.6 GHz, respectively. (C) 2009 Elsevier Ltd. All rights reserved.