A semiconductor device includes a first semiconductor layer on one main surface of a semiconductor substrate; a plurality of trench gates in the first semiconductor layer extending to reach the inside of the semiconductor substrate; a second semiconductor layer selectively provided in an upper portion of the first semiconductor layer between the trench gates; an isolation layer in contact with a side surface of the second semiconductor layer and extends in the first semiconductor; and a third semiconductor layer in the upper portion of the first semiconductor layer between the trench gates and has at least one side surface in contact with the trench gate. The isolation layer is between and separates the second semiconductor layer and the third semiconductor layer from each other and is formed to extend to the same depth as, or to a position deeper than the second semiconductor layer.