| 摘要 |
PROBLEM TO BE SOLVED: To reduce an off-current of a thin film transistor in which an oxide semiconductor is used for a channel formation region.SOLUTION: A thin film transistor comprises an oxide semiconductor layer used for a channel formation region. The oxide semiconductor layer has a face controlled in oxygen density on the side opposite to a gate insulator layer (backchannel side), where the oxide semiconductor layer is in contact with an insulative film making a protection film. That is, the oxygen density of the face of the oxide semiconductor layer on the backchannel side is made higher to reduce an off-current. By making higher the oxygen density of the oxide semiconductor, the production of microcrystalline is suppressed and the oxide semiconductor becomes amorphous. The amorphized high-oxygen density region in the oxide semiconductor has a high resistance. So, the region is hard to pass electric current therethrough.SELECTED DRAWING: Figure 1 |
