A method (and resultant structure) includes forming a semiconductor layer having plural stripe-like trenches, forming a gate electrode buried partially in each of the plural trenches, and introducing an impurity into the semiconductor layer by ion implantation after forming the gate electrode. The gate electrode has a buried portion formed in each of the trenches and a protruding portion situating above the buried portion and having a width larger than that of the buried portion. The introducing the impurity includes introducing an impurity into the semiconductor layer below the protruding portion by oblique ion implantation.