US Patent 11430896 Semiconductor device and manufacturing method thereof

A semiconductor device capable of high speed operation is provided. Further, a highly reliable semiconductor device is provided. An oxide semiconductor having crystallinity is used for a semiconductor layer of a transistor. A channel formation region, a source region, and a drain region are formed in the semiconductor layer. The source region and the drain region are formed in such a manner that one or more of elements selected from rare gases and hydrogen are added to the semiconductor layer by an ion doping method or an ion implantation method with the use of a channel protective layer as a mask.