Memory device with semiconductor elements
View Patent ↗A dynamic flash memory includes a p layer as a semiconductor base material, first and second n + layers on opposite sides thereof, first and second gate insulating layers in contact with each other and partially covering the p layer, and first and second gate conductor layers electrically isolated from each other and respectively provided on the first and second gate insulating layers. The first and second n + layers and first and second gate conductor layers are respectively connected to source, bit, word, and plate lines. During writing, 1.0 V, 1.5 V, and 1.2 V are sequentially applied to the bit, plate, and word lines, respectively. During erasing, 2 V is applied to the plate line, and then, a voltage applied to each terminal is always set 0 V or greater (e.g., 0.6 V for the bit line). Further, during reading, voltages are sequentially applied to the bit, plate, and word lines.
1. A memory device with semiconductor elements, comprising:
a semiconductor base material extending on a substrate in a horizontal direction or a vertical direction;
a first impurity layer and a second impurity layer that are continuous with respective opposite ends of the semiconductor base material;
a first gate insulating layer partially covering the semiconductor base material;
a first gate conductor layer covering the first gate insulating layer;
a second gate insulating layer partially covering the semiconductor base material; and
a second gate conductor layer not in contact with the first gate conductor layer, the second gate conductor layer covering the second gate insulating layer,
wherein a memory write operation is performed by first applying a first voltage to allow a potential difference to be generated between the first impurity layer and the second impurity layer, and then applying second and third voltages each having the same polarity as a polarity of the first voltage to the first gate conductor layer and the second conductor layer, respectively, thereby increasing majority carriers in the semiconductor base material through an impact ionization phenomenon,
a memory erase operation is performed by first applying a fourth voltage to one of the first gate conductor layer and the second gate conductor layer, and then applying a fifth voltage having the same polarity as a polarity of the fourth voltage to allow a potential difference to be generated between the first impurity layer and the second impurity layer, thereby reducing majority carriers remaining in the semiconductor base material, and
a memory read operation is performed by first applying a sixth voltage to allow a potential difference to be generated between the first impurity layer and the second impurity layer, and then applying a seventh voltage to one of the first gate conductor layer and the second gate conductor layer, and thereafter applying an eighth voltage having the same polarity as a polarity of the seventh voltage to another of the first gate conductor layer and the second gate conductor layer.
2. The memory device with the semiconductor elements according to claim 1 ,
wherein the first impurity layer is connected to a source line, the second impurity layer is connected to a bit line, one of the first gate conductor layer and the second gate conductor layer is connected to a word line, and another of the first gate conductor layer and the second gate conductor layer is connected to a plate line, and
an operation of a dynamic flash memory is performed by applying a voltage to each of the source line, the bit line, the plate line, and the word line to execute the memory write operation, the memory read operation, and the memory erase operation.
3. The memory device with the semiconductor elements according to claim 2 ,
wherein the write operation for the dynamic flash memory includes
applying the first voltage to one of the first impurity layer and the second impurity layer to allow a potential difference to be generated between the first impurity layer and the second impurity layer, and
then applying the second voltage to one of the first gate conductor layer and the second gate conductor layer, the second voltage having the same polarity as a polarity of the first voltage and having an absolute value greater than an absolute value of a threshold voltage of a transistor including the gate conductor layer, and
then applying the third voltage to another of the first gate conductor layer and the second gate conductor layer, the third voltage having the same polarity as a polarity of the first voltage and having an absolute value greater than an absolute value of a threshold voltage of a transistor including the gate conductor layer.
4. The memory device with the semiconductor elements according to claim 2 ,
wherein the write operation for the dynamic flash memory includes, before lowering the first voltage applied to the first impurity layer or the second impurity layer, lowering the second and third voltages applied to the first gate conductor layer and the second gate conductor layer, respectively.
5. The memory device with the semiconductor elements according to claim 2 ,
wherein the erase operation for the dynamic flash memory includes
applying the fourth voltage to one of the first gate conductor layer and the second gate conductor layer, the fourth voltage having the same polarity as a polarity of a threshold voltage of a transistor including the gate conductor layer and having an absolute value greater than an absolute value of the threshold voltage, and
then applying the fifth voltage having the same polarity as a polarity of the fourth voltage to allow a potential difference to be generated between the first impurity layer and the second impurity layer, thereby reducing majority carriers remaining in the semiconductor base material.
6. The memory device with the semiconductor elements according to claim 2 , wherein the read operation for the dynamic flash memory includes
applying the sixth voltage to allow a potential difference to be generated between the first impurity layer and the second impurity layer, and
then applying the seventh voltage to one of the first gate conductor layer and the second gate conductor layer, the seventh voltage having a level between a threshold voltage for the memory writing operation and a threshold voltage for the memory erasing operation of a transistor including the gate conductor layer, and
thereafter applying the eighth voltage to another of the first gate conductor layer and the second gate conductor layer, the eighth voltage having the same polarity as a polarity of the seventh voltage and having an absolute value greater than an absolute value of a threshold voltage for erasing of a transistor including the gate conductor layer.
7. The memory device with the semiconductor elements according to claim 2 ,
wherein in each of the write operation, the erase operation, and the read operation for the dynamic flash memory, when majority carriers in the semiconductor base material are holes, a voltage of 0 V or a positive potential is applied to the first impurity layer, the second impurity layer, the first gate conductor layer, and the second gate conductor layer.
8. The memory device with the semiconductor elements according to claim 2 ,
wherein in each of the write operation, the erase operation, and the read operation for the dynamic flash memory, when majority carriers in the semiconductor base material are electrons, a voltage of 0 V or a negative potential is applied to the first impurity layer, the second impurity layer, the first gate conductor layer, and the second gate conductor layer.
9. The memory device with the semiconductor elements according to claim 2 ,
wherein an absolute value of a current flowing through the bit line during the memory erase operation for the dynamic flash memory is lower than an absolute value of a current flowing through the bit line during the memory write operation for the dynamic flash memory.
10. The memory device with the semiconductor elements according to claim 2 ,
wherein the voltages applied to the plate line, the word line, the source line, and the bit line during the memory write operation, the memory erase operation, and the memory read operation for the dynamic flash memory are 0 V or voltages having the same polarity.
11. The memory device with the semiconductor elements according to claim 2 ,
wherein in the memory write operation for the dynamic flash memory, a maximum electric field generated in the semiconductor base material due to the potential difference generated between the first impurity layer and the second impurity layer is greater than or equal to 10 5 V/cm.
12. The memory device with the semiconductor elements according to claim 2 ,
wherein in the memory erase operation for the dynamic flash memory, a maximum electric field generated in the semiconductor base material due to the potential difference generated between the first impurity layer and the second impurity layer is greater than or equal to 10 4 V/cm.
13. The memory device with the semiconductor elements according to claim 2 ,
wherein in the memory read operation for the dynamic flash memory, a maximum electric field generated in the semiconductor base material due to the potential difference generated between the first impurity layer and the second impurity layer is greater than or equal to 10 5 V/cm.