In a manufacturing method of a semiconductor device, a trench is defined in a semiconductor substrate, and an adjuster layer having a first conductivity type impurity concentration higher than a drift layer is formed at a portion of the semiconductor substrate adjacent to a bottom wall of the trench. A channel layer is formed by introducing second conductivity type impurities to a portion of the semiconductor substrate adjacent to a sidewall of the trench and between the adjustment layer and a main surface of the semiconductor substrate while restricting the channel layer from extending in a depth direction of the trench by the adjustment layer.