A semiconductor layer may be subjected to etching to form a trench therein. An epitaxial layer may be further formed in the trench. Here, the impurity concentration of the epitaxial layer is controlled to be lower than that of the semiconductor layer. In this manner, concentration of electrical fields in the trench is reduced. A first innovations herein provides a semiconductor device including a first semiconductor layer containing impurities of a first conductivity type, a trench provided in the first semiconductor layer on a front surface side thereof, and a second semiconductor layer provided on an inner wall of the trench, where the second semiconductor layer contains impurities of the first conductivity type at a lower concentration than the first semiconductor layer.