A semiconductor device disclosed herein includes an insulated gate, a main and a sub trench conductors. The main and sub trench conductors are formed in the cell region, and have a conductor that is covered with an insulation film and fills a trench extending in a first direction. The sub trench is located, with respect to the main trench conductor, in a second direction perpendicularly crossing the first direction and extending from the cell region side to the non-cell region. Length of the sub trench conductor in the first direction is shorter than a length of the insulated gate in the first direction. Distance between the main and sub trench conductors is shorter than a distance between the main trench conductor and the insulated gate. At least a part of the sub trench conductor reaches a position deeper than a boundary between the first and second semiconductor regions.