Low off-state leakage current semiconductor memory device
First Claim
1. A semiconductor device comprising:
- a source line;
n bit lines, n being a natural number;
m memory cells electrically connected in series between the source line and the bit lines, m being a natural number;
m+1 word lines;
a first selection line and a second selection line;
a first selection transistor comprising a gate electrode electrically connected to the first selection line; and
a second selection transistor comprising a gate electrode electrically connected to the second selection line;
wherein the memory cells each comprises;
a first transistor comprising a substrate including a semiconductor material, a first gate electrode, a first source electrode, and a first drain electrode;
a second transistor comprising an oxide semiconductor layer, a second gate electrode, a second source electrode, and a second drain electrode; and
a capacitor,wherein the source line is electrically connected to the first source electrode in a m-th memory cell through the second selection transistor,wherein a first bit line is electrically connected to the first drain electrode of a first memory cell through the first selection transistor and is electrically connected to the second drain electrode of the first memory cell,wherein a first word line is electrically connected to the second gate electrode of the first memory cell,wherein a k-th word line is electrically connected to the second gate electrode of a k-th memory cell and is electrically connected to one electrode of the capacitor in a (k−
1)-th memory cell, k being a natural number of greater than or equal to 2 and less than or equal to m,wherein the first drain electrode of the k-th memory cell is electrically connected to the first source electrode of the (k−
1)-th memory cell, andwherein the first gate electrode of the m-th memory cell, the second source electrode of the m-th memory cell, and the other electrode of the capacitor of the m-th memory cell are electrically connected to one other.
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Accused Products
Abstract
An object is to provide a semiconductor device which can hold stored data even when not powered and which achieves high integration by reduction of the number of wirings. The semiconductor device is formed using a material which can sufficiently reduce the off-state current of a transistor, e.g., an oxide semiconductor material which is a wide bandgap semiconductor. When a semiconductor material which allows a sufficient reduction in the off-state current of a transistor is used, data can be held for a long period. One line serves as the word line for writing and the word line for reading and one line serves as the bit line for writing and the bit line for reading, whereby the number of wirings is reduced. Accordingly, the storage capacity per unit area is increased.
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Citations
20 Claims
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1. A semiconductor device comprising:
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a source line; n bit lines, n being a natural number; m memory cells electrically connected in series between the source line and the bit lines, m being a natural number; m+1 word lines; a first selection line and a second selection line; a first selection transistor comprising a gate electrode electrically connected to the first selection line; and a second selection transistor comprising a gate electrode electrically connected to the second selection line; wherein the memory cells each comprises; a first transistor comprising a substrate including a semiconductor material, a first gate electrode, a first source electrode, and a first drain electrode; a second transistor comprising an oxide semiconductor layer, a second gate electrode, a second source electrode, and a second drain electrode; and a capacitor, wherein the source line is electrically connected to the first source electrode in a m-th memory cell through the second selection transistor, wherein a first bit line is electrically connected to the first drain electrode of a first memory cell through the first selection transistor and is electrically connected to the second drain electrode of the first memory cell, wherein a first word line is electrically connected to the second gate electrode of the first memory cell, wherein a k-th word line is electrically connected to the second gate electrode of a k-th memory cell and is electrically connected to one electrode of the capacitor in a (k−
1)-th memory cell, k being a natural number of greater than or equal to 2 and less than or equal to m,wherein the first drain electrode of the k-th memory cell is electrically connected to the first source electrode of the (k−
1)-th memory cell, andwherein the first gate electrode of the m-th memory cell, the second source electrode of the m-th memory cell, and the other electrode of the capacitor of the m-th memory cell are electrically connected to one other. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A semiconductor device comprising:
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a source line; n bit lines, n being a natural number; m memory cells electrically connected in series between the source line and the bit lines, m being a natural number; m+1 word lines; a first selection line and a second selection line; a first selection transistor comprising a gate electrode electrically connected to the first selection line; and a second selection transistor comprising a gate electrode electrically connected to the second selection line; wherein the memory cells each comprises; a first transistor comprising a substrate including a semiconductor material, a first gate electrode, a first source electrode, and a first drain electrode; a second transistor comprising an oxide semiconductor layer, a second gate electrode, a second source electrode, and a second drain electrode; and a capacitor including the second source electrode, the oxide semiconductor, the second gate insulating layer, an insulating layer over the second gate insulating layer and an electrode over the insulating layer, wherein the source line is electrically connected to the first source electrode in a m-th memory cell through the second selection transistor, wherein a first bit line is electrically connected to the first drain electrode of a first memory cell through the first selection transistor and is electrically connected to the second drain electrode of the first memory cell, wherein a first word line is electrically connected to the second gate electrode of the first memory cell, wherein a k-th word line is electrically connected to the second gate electrode of a k-th memory cell and is electrically connected to one electrode of the capacitor in a (k−
1)-th memory cell, k being a natural number of greater than or equal to 2 and less than or equal to m,wherein the first drain electrode of the k-th memory cell is electrically connected to the first source electrode of the (k−
1)-th memory cell, andwherein the first gate electrode of the m-th memory cell, the second source electrode of the m-th memory cell, and the other electrode of the capacitor of the m-th memory cell are electrically connected to one other. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification