Transistor, semiconductor device, and electronic device
摘要
說明書
Furthermore, the gate electrode and the back gate electrode are formed using conductive layers and thus each have a function of preventing an electric field generated outside the transistor from influencing the semiconductor layer where the channel is formed (in particular, an electric field blocking function against static electricity and the like). When the back gate electrode is formed larger than the semiconductor layer to cover the semiconductor layer in the plan view, the electric field blocking function can be enhanced.
Since the electrodes 105_1 and 112_1 each have a function of blocking an electric field from the outside, charges of charged particles and the like generated over the electrode 112_1 or under the electrode 105_1 do not influence the channel formation region in the semiconductor layer 109_1b. Thus, degradation by a stress test (e.g., a negative gate bias temperature (?GBT) stress test in which negative charges are applied to a gate) can be reduced. In addition, the electrodes 105_1 and 112_1 can block an electric field generated from the drain electrode so as not to affect the semiconductor layer. Thus, changes in the rising voltage of on-state current due to changes in drain voltage can be suppressed. Note that this effect is significant when a potential is applied to the electrodes 105_1 and 112_1.
