To realize high performance and low power consumption of a semiconductor device by controlling electric characteristics of a transistor in accordance with a required function. Further, to manufacture such a semiconductor device with high yield and high productivity without complicating a manufacturing process. An impurity element imparting one conductivity type is added to a first semiconductor wafer in order to control the threshold voltage of a transistor included in the semiconductor device, before separating a single crystal semiconductor layer used as a channel formation region of the transistor from the first semiconductor wafer and transferring the single crystal semiconductor layer to a second semiconductor wafer.