US Patent 7645661 Semiconductor device

A semiconductor device manufactured by forming a plurality of first trenches in each of which a trench gate is formed, in an epitaxial layer of a first conductivity type; implanting an impurity of a second conductivity type into a part beneath each of the first trenches to form a first column region; and implanting an impurity of the second conductivity type into a part beneath a base region formed between the first trenches to form a second column region. The first and second column regions are formed with an impurity concentration such that a total depletion charge in the regions is substantially equal to a depletion charge in the epitaxial layer.