Semiconductor device

An element isolation trench is formed in a substrate and is formed along each side of a polygon in a planar view. A first trench is formed in the substrate and extends in a direction different from that of any side of the trench. A first-conductivity type region is formed on/over apart located on the side of an end of the first trench in the substrate. Accordingly, when an impurity region that extends in a depth direction in the substrate is formed by forming the trench in the substrate and diagonally implanting an impurity into the trench, the impurity is prevented from being implanted into a side face of a groove such as a groove for element isolation and so forth impurity implantation into the side face of which is not desired.