In our previous study, the on-resistance of the SiC-based vertical MOSFET had been reduced in double-epitaxial MOSFET (DEMOSFET). The device exhibited an on-resistance (Rons) of 8.5 mWcm2 with a blocking voltage (Vbr) of 600 V. This study analyzed the characteristics of the DEMOSFET using a numerical simulation. The results showed the trade-off relationship between the specific on-resistance and the blocking characteristics when the concentration of the nitrogen ions increases in the surface of the n-type region between the p-wells. Specially, the specific on-resistance was drastically improved by increasing the concentration of the nitrogen ions. The thick gate oxide on the n-type region between the p-wells had an advantage to suppress the electric field in the gate oxide.