A lower doped layer is inserted between the gate and channel layer and its effect on the performance of a 4H-SiC Schottky barrier field-effect transistor(MESFET) is investigated.The dependences of the drain current and small signal parameters on this inserted gate-buffer layer are obtained by solving one-dimensional(1-D) and two-dimensional(2-D) Poisson’s equations.The drain current and small signal parameters of the 4H-SiC MESFET with a gate-buffer layer thickness of 0.15μm are calculated and the breakdown characteristics are simulated.The results show that the current is increased by increasing the thickness of the gate-buffer layer;the breakdown voltage is 160 V,compared with 125 V for the conventional 4H-SiC MESFET;the cutoff frequency is 27 GHz,which is higher than 20 GHz of the conventional structure due to the lower doped gate-buffer layer. A lower doped layer is inserted between the gate and channel layer and its effect on the performance of a 4H-SiC Schottky barrier field-effect transistor (MESFET) is investigated. The dependences of the drain current and small signal parameters on this inserted gate- buffer layer are obtained by solving one-dimensional (1-D) and two-dimensional (2-D) Poisson’s equations. drain current and small signal parameters of the 4H-SiC MESFET with a gate-buffer layer thickness of 0.15 μm are calculated and the breakdown characteristics are simulated. The results show that the current is increased by increasing the thickness of the gate-buffer layer; the breakdown voltage is 160 V, compared with 125 V for the conventional 4H-SiC MESFET; 27 GHz, which is higher than 20 GHz of the conventional structure due to the lower doped gate-buffer layer.