Electric power consumption seems to increase continuously for long term in the future. Consequently, effective use of electric power becomes very important issue. The key technology for this issue is conversion of the electric power using power semiconductor devices. However, performance of existing silicon (Si) based device is approaching to its theoretical limit. Silicon carbide (4H-SiC) based vertical MOS transistor (MOSFET) is one of promising candidates for high-power unipolar switching device because 4H-SiC has superior physical and electrical properties. However, vertical MOSFETs on 4H-SiC showed high on-resistance due to the poor channel mobility on the implanted rough surface. In this study, we developed a novel 4H-SiC vertical MOSFET employing two epitaxially grown layers as a MOS channel region. We named it double-epitaxial MOSFET (DEMOSFET). Fabricated device exhibits a ultra-low specific on-resistance (Rons) of 7.7 mΩcm² with a blocking voltage of 600 V. This is the first Rons lower than 10 mΩcm².