| 摘要 |
A highly reliable semiconductor device exhibiting stable electrical characteristics is provided. Further, a highly reliable semiconductor device is provided. Oxide semiconductor films are stacked so that the conduction band has a well-shaped structure. Specifically, a transistor having a multi-layer structure is manufactured in which a second oxide semiconductor film having a crystalline structure is stacked over a first oxide semiconductor film, and at least a third oxide semiconductor film is provided over the second oxide semiconductor film. When a buried channel is formed in the transistor, few oxygen vacancies are generated and the reliability of the transistor is improved. |
