Memory device and semiconductor device
An object of one embodiment of the present invention is to propose a memory device in which a period in which data is held is ensured and memory capacity per unit area can be increased. In the memory device of one embodiment of the present invention, bit lines are divided into groups, and word lines are also divided into groups. The word lines assigned to one group are connected to the memory cell connected to the bit lines assigned to the one group. Further, the driving of each group of bit lines is controlled by a dedicated bit line driver circuit of a plurality of bit line driver circuits. In addition, cell arrays are formed on a driver circuit including the above plurality of bit line driver circuits and a word line driver circuit. The driver circuit and the cell arrays overlap each other.
1. A memory device comprising:
a substrate;
a first cell array comprising first memory cells formed over the substrate;
a second cell array comprising second memory cells formed over the substrate;
a first bit line driver circuit formed over the substrate;
a second bit line driver circuit formed over the substrate; and
a word line driver circuit formed over the substrate,
wherein the first bit line driver circuit is electrically connected to the first cell array,
wherein the second bit line driver circuit is electrically connected to the second cell array,
wherein the word line driver circuit is electrically connected to the first cell array and the second cell array,
wherein the first cell array and the second cell array overlap with the first bit line driver circuit and the second bit line driver circuit, respectively.
2. The memory device according to claim 1 , wherein the first memory cells and second memory cells comprise transistors comprising a channel formation region in an oxide semiconductor film formed over the substrate.
3. The memory device according to claim 1 , wherein an aluminum oxide layer is interposed between the memory cell and the substrate.
4. A semiconductor device comprising the memory device according to claim 1 .
5. The memory device according to claim 1 , wherein the first bit line driver circuit is provided adjacently to the second bit line driver circuit.
6. A memory device comprising:
a semiconductor substrate;
a cell array comprising memory cells formed over the semiconductor substrate; and
a bit line driver circuit formed over the semiconductor substrate;
wherein the memory cell comprises a first transistor and a capacitor,
wherein the bit line driver circuit comprises a second transistor,
wherein one of a source electrode and a drain electrode of the first transistor is electrically connected to the bit line driver circuit,
wherein other of the source electrode and the drain electrode of the first transistor is electrically connected to a first electrode of the capacitor,
wherein the first electrode of the capacitor is over a second electrode of the capacitor,
wherein the first transistor comprises a channel formation region in an oxide semiconductor film formed over the semiconductor substrate,
wherein the second transistor comprises a channel formation region in the semiconductor substrate, and
wherein the cell array overlaps with the bit line driver circuit.
7. The memory device according to claim 6 , wherein the semiconductor substrate is not formed from an oxide semiconductor material.
8. The memory device according to claim 6 , wherein an aluminum oxide layer is interposed between the oxide semiconductor film and the semiconductor substrate.
9. A semiconductor device comprising the memory device according to claim 6 .
10. A memory device comprising:
a semiconductor substrate;
a first cell array comprising first memory cells formed over the semiconductor substrate;
a second cell array comprising second memory cells formed over the semiconductor substrate; and
a driver circuit comprising:
a third transistor;
a first bit line driver circuit;
a second bit line driver circuit; and
a word line driver circuit,
wherein the first memory cell comprises first transistor,
wherein the second memory cell comprises second transistor,
wherein one of a source and a drain of the first transistor is electrically connected to the first bit line driver circuit,
wherein a gate of the first transistor is electrically connected to the word line driver circuit,
wherein one of a source and a drain of the second transistor is electrically connected to the second bit line driver circuit,
wherein a gate of the second transistor is electrically connected to the word line driver circuit,
wherein the first transistor comprises a channel formation region in an oxide semiconductor film formed over the semiconductor substrate,
wherein the second transistor comprises a channel formation region in an oxide semiconductor film formed over the semiconductor substrate,
wherein the third transistor comprises a channel formation region in the semiconductor substrate, and
wherein the first transistor and the second transistor are over the third transistor.
11. The memory device according to claim 10 , wherein the semiconductor substrate is not formed from an oxide semiconductor material.
12. The memory device according to claim 10 , wherein the channel formation region of the third transistor is comprised in polycrystalline silicon, single crystal silicon, polycrystalline germanium, or single crystal germanium.
13. The memory device according to claim 10 , wherein an aluminum oxide layer is interposed between the oxide semiconductor film and the semiconductor substrate.
14. A semiconductor device comprising the memory device according to claim 10 .