| 摘要 |
PROBLEM TO BE SOLVED: To provide a storage device capable of retaining data for a long period of time.SOLUTION: A storage device 100 comprises: memory element (capacitative element 102, transistor 103); and a transistor 101 which functions as a switching element for controlling supply, retention and discharge of charge in the memory elements. The transistor 101 includes a second gate electrode for controlling threshold voltage other than a normal gate electrode, and since the transistor 101 includes an oxide semiconductor in an active layer, off-state current is extremely low. The storage device 100 stores data by controlling charge amounts of the memory elements 102, 103 via the transistor 101 having extremely low off-state current instead of injecting charge to a floating gate surrounded by an insulation film at high voltage. |
