| abstract |
A gate electrode configured to apply a gate voltage, a source electrode and a drain electrode configured to transmit an electric signal, an active layer formed between the source electrode and the drain electrode, and a gate insulating layer formed between the gate electrode and the active layer Wherein the active layer includes at least two kinds of oxide layers including an A layer and a B layer, and the active layer has the following conditions (1) and (2): Condition (1): the active layer includes three or more oxide layers including two or more A layers, and Condition (2): the band gap of the A layer is smaller than the band gap of the B layer, and the oxygen affinity of the A layer is equal to or higher than the oxygen affinity of the B layer Of the first conductivity type. |