Abstract: A semiconductor device has source and drain regions, a gate insulating film, a gate electrode, and a channel region. The channel region includes a region where carriers move between the source and drain regions. An impurity concentration of the channel region is higher at an end portion of a surface depletion layer than at an interface between the semiconductor layer and the gate insulating film. The impurity concentration varies along a direction in which the gate electrode, the gate insulating film and the channel region are successively provided, and it increases substantially linearly near the end portion of the surface depletion layer.