The semiconductor device includes: a substrate, an n-type drift region formed on a main surface of the substrate; a p-type well region, an n-type drain region and an n-type source region each formed in the drift region to extend from a second main surface of the drift region opposite to the first main surface of the drift region in contact with the substrate in a direction perpendicular to the second main surface; a gate groove extending from the second main surface in the perpendicular direction and penetrating the source region and the well region in a direction parallel to the first main surface of the substrate; and a gate electrode formed on a surface of the gate groove with a gate insulating film interposed therebetween, wherein the drift region has a higher impurity concentration than the substrate, and the well region extends to the inside of the substrate.