Manufacturing a semiconductor device with higher operating characteristics and achieve low power consumption of a semiconductor integrated circuit. A single crystal semiconductor layer is formed so that crystal plane directions of single crystal semiconductor layers which are used for channel regions of an n-channel TFT and a p-channel TFT and which are formed over the same plane of the substrate are the most appropriate crystal plane directions for each TFT. In accordance with such a structure, mobility of carrier flowing through a channel is increased and the semiconductor device with higher operating characteristics can be provided. Low voltage driving can be performed, and low power consumption can be achieved.