A semiconductor device with a simplified structure including an energization control element and reverse coupling protection element, and a manufacturing method therefor. Its semiconductor substrate has deep and shallow trenches in its first surface. A first n-type impurity region lies in its second surface in contact with the deep trench bottom. A p-type impurity region includes: a p-type base region to make a pn junction with the first n-type region and in contact with the shallow trench bottom; and a back gate region joined to the p-type base region, lying in the first surface. A second n-type impurity region makes a pn junction with the p-type impurity region, lying in the first surface in contact with the shallow trench side face. An n+ source region makes a pn junction with the p-type region, lying in the first surface in contact with the side faces of deep and shallow trenches.