| 摘要 |
To provide a thin film transistor which has high operation speed and in which a large amount of current can flow when the thin film transistor is on and off-state current at the time when the thin film transistor is off is extremely reduced. The thin film transistor is a vertical thin film transistor in which a channel formation region is formed using an oxide semiconductor film in which hydrogen or an OH group contained in the oxide semiconductor is removed so that hydrogen is contained in the oxide semiconductor at a concentration of lower than or equal to 5×1019/cm3, preferably lower than or equal to 5×1018/cm3, more preferably lower than or equal to 5×1017/cm3, and the carrier concentration is lower than or equal to 5×1014/cm3, preferably lower than or equal to 5×1012/cm3. |
