In general, this disclosure describes a semiconductor device that exhibits an increased resistance and reduced leakage current in a reverse-biased state, and a method for manufacturing such a semiconductor device. For example, in one embodiment, the increased resistance in the reverse-biased state is obtained by introducing either a P+ or P- type impurity in a polycrystalline silicon layer formed on an N- type epitaxial layer. Additionally, the semiconductor device maintains a low resistance in a forward-biased state. To keep the forward-biased resistance low, the polycrystalline silicon layer in the vicinity of a gate electrode may be of an N+ type. Furthermore, an N+ type source extracting region is formed on the surface of the polycrystalline silicon layer to connect a source electrode to a drain electrode and maintain a low resistance when forward-biased.