A stack including at least an insulating layer, a first electrode, and a first impurity semiconductor layer is provided over a supporting substrate; a first semiconductor layer to which an impurity element imparting one conductivity type is added is formed over the first impurity semiconductor layer; a second semiconductor layer to which an impurity element imparting the one conductivity type is added is formed over the first semiconductor layer under a condition different from that of the first semiconductor layer; crystallinity of the first semiconductor layer and crystallinity of the second semiconductor layer are improved by a solid-phase growth method to form a second impurity semiconductor layer; an impurity element imparting the one conductivity type and an impurity element imparting a conductivity type different from the one conductivity type are added to the second impurity semiconductor layer; and a gate electrode layer is formed via a gate insulating layer.