MEMORY DEVICE AND SEMICONDUCTOR DEVICE
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Abstract
A memory device in which data can be retained for a long time is provided. The memory device includes a memory element and a transistor which functions as a switching element for controlling supply, storage, and release of electrical charge in the memory element. The transistor includes a second gate electrode for controlling the threshold voltage in addition to a normal gate electrode. Further, the off-state current of the transistor is extremely low because an active layer thereof includes an oxide semiconductor. In the memory device, data is stored not by injection of electrical charge to a floating gate surrounded by an insulating film at high voltage but by control of the amount of electrical charge of the memory element through the transistor whose off-state current is extremely low.
13 Citations
17 Claims
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1. (canceled)
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2. A driving method for a semiconductor device, the semiconductor device comprising:
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a transistor comprising an oxide semiconductor layer, a first gate electrode, and a second gate electrode; and a memory element electrically connected to the oxide semiconductor layer, wherein the oxide semiconductor layer is interposed between the first gate electrode and the second gate electrode, the driving method comprising; applying a first potential to the first gate electrode and a second potential to the second gate electrode, respectively, during a first period; and applying a third potential to the first gate electrode and a fourth potential to the second gate electrode, respectively, during a second period, wherein the first potential is configured to be higher than or equal to the second potential, wherein the first potential is configured to be higher than or equal to the third potential, wherein the second potential is configured to be higher than or equal to the fourth potential, wherein the third potential is configured to be higher than or equal to the fourth potential, and wherein the second potential is configured to be lower than or equal to the third potential. - View Dependent Claims (3, 4, 5, 6, 7)
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8. A driving method for a semiconductor device, the semiconductor device comprising:
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a first transistor comprising an oxide semiconductor layer, a first gate electrode, and a second gate electrode; a second transistor comprising a gate electrode, a source electrode and a drain electrode; and a capacitor comprising a first electrode and a second electrode, the first electrode being electrically connected to the oxide semiconductor layer and the gate electrode, wherein the oxide semiconductor layer is interposed between the first gate electrode and the second gate electrode, the driving method comprising; applying a first potential to the first gate electrode, a second potential to the second gate electrode and a third potential to the second electrode, respectively, during a first period; applying a fourth potential to the first gate electrode, a fifth potential to the second gate electrode and a sixth potential to the second electrode, respectively, during a second period; and applying the fourth potential to the first gate electrode, the fifth potential to the second gate electrode and the third potential to the second electrode, respectively, during a third period, wherein the first potential is configured to be higher than or equal to the second potential, wherein the first potential is configured to be higher than or equal to the fourth potential, wherein the second potential is configured to be higher than or equal to the fifth potential, wherein the third potential is configured to be lower than the sixth potential, and wherein the second potential is configured to be lower than or equal to the fourth potential. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification