| 摘要 |
PROBLEM TO BE SOLVED: To provide a transistor that can be driven at a high operation frequency.SOLUTION: A transistor comprises: first to third oxide semiconductor layers, a gate insulating layer, a gate electrode layer, and a portion in which the first oxide semiconductor layer, the second oxide semiconductor layer, and the third oxide semiconductor layer are laminated in this order. The channel length of the transistor is less than 100 nm. The cutoff frequency is higher than 1 GHz where the source-drain voltage is 1 V or higher and 2 V or lower. The gate insulating layer is in contact with the upper surface of the third oxide semiconductor layer. The gate electrode layer has a region overlapping the portion mentioned above via the gate insulating layer. The second oxide semiconductor layer has a plurality of crystal portions oriented to the c-axis and has a region in which the hydrogen concentration measured by secondary ion mass spectrometry is less than 2×10atoms/cm.SELECTED DRAWING: Figure 20 |
