Semiconductor device and manufacturing method thereof

A semiconductor device includes: a drift region that is arranged on a main surface of a substrate, and has a higher impurity concentration than the substrate; a first well region that is connected to the drift region; and a second well region that is arranged adjacent to the first well region and faces the drift region. The second well region has a higher impurity concentration than the first well region. A distance between the source region that faces the drift region via the first well region and the drift region is greater than a distance between the second well region and the drift region, in a direction parallel to the main surface of the substrate. A depletion layer extending from the second well region reaches the drift region.