Abstract: Drain-induced barrier lowering effect（DIBL effect） on the subthreshold behavior is studied in 6H^- and 4H-SiC MESFET’s through an analytical two-dimensional model.Based on the physical analysis,the temperature dependences of channel potential,threshold voltage and subthreshold current for 6H^- and 4H-SiC MESFET’s are investigated.The simulation results show that as the existence of DIBL effect,the channel potential minimum varies with the gate length and temperature,bringing the variation of threshold voltage and the subthreshold current of SiC MESFETs.In addition,the subthreshold slope factor N_s is inversely proportional to the gate length and temperature.The smaller Ns indicates that the gate voltage strongly controls the drain current,finally,bringing a larger slope of the linear part in the logIds-Vgs relationship.