An object is to provide a manufacturing method of a semiconductor device having a high field effect mobility and including an oxide semiconductor layer in a semiconductor device including an oxide semiconductor. Another object is to provide a manufacturing method of a semiconductor device capable of high speed operation. An oxide semiconductor layer is terminated by a halogen element, and thus an increase in the contact resistance between the oxide semiconductor layer and a conductive layer in contact with the oxide semiconductor layer is suppressed. Therefore, the contact resistance between the oxide semiconductor layer and the conductive layer becomes favorable and a transistor having a high field effect mobility can be manufactured.