Semiconductor storage device
A semiconductor storage device includes: a cell array including a plurality of first wirings, a plurality of second wirings intersecting the first wirings, and memory cells positioned at intersecting portions between the first wirings and the second wirings, each of the memory cells having a series circuit of a non-ohmic element and a variable resistance element; a control circuit configured to apply a control voltage, which is necessary for the variable resistance element to transit from a low resistance state to a high resistance state, to the memory cells through the first wirings and the second wirings; and a bias voltage application circuit configured to apply a bias voltage, which suppresses a potential variation caused by the transition of the variable resistance element from the low resistance state to the high resistance state, to one end of the variable resistance element.
1. A semiconductor storage device comprising:
a cell array including a plurality of first wirings, a plurality of second wirings intersecting the first wirings, and memory cells positioned at intersecting portions between the first wirings and the second wirings, each of the memory cells having a variable resistance element;
a control circuit configured to apply a first voltage to one of the first wirings and a second voltage lower than the first voltage to one of the second wirings; and
a bias voltage application circuit including a dummy memory cell positioned at an intersecting portion between another one of the first wirings and the one of the second wirings, and a dummy wiring control circuit configured to apply a dummy wiring control voltage to the other one of the first wirings when the control circuit applies the first voltage to the one of the first wirings.
2. The semiconductor storage device according to claim 1 , wherein the dummy wiring control voltage suppresses a potential variation of the one of the second wirings connected to a selected variable resistance element.
3. The semiconductor storage device according to claim 2 , wherein the bias voltage application circuit outputs a voltage, which is larger than a voltage obtained by subtracting a voltage by which the memory cells transit from a high resistance state to a low resistance state from the first voltage applied to the one of the first wirings, as the dummy wiring control voltage.
4. The semiconductor storage device according to claim 2 , wherein the bias voltage application circuit keeps the dummy wiring control voltage by increasing a current flowing to the other one of the first wirings when the memory cells transit from a low resistance state to a high resistance state.
5. The semiconductor storage device according to claim 2 , wherein the dummy memory cell is disposed in an end portion of the one of the second wirings.
6. The semiconductor storage device according to claim 2 , wherein the dummy memory cell is a memory cell permanently placed in a low resistance state by breaking the variable resistance element.
7. The semiconductor storage device according to claim 1 , wherein the bias voltage application circuit comprises:
a constant current circuit configured to supply a constant current to the other one of the first wirings when the control circuit applies the first voltage to the one of the first wirings;
a sampling circuit configured to sample a potential on the other one of the first wirings just after the constant current circuit supplies the constant current to the other one of the first wirings; and
an amplifying circuit configured to keep the potential on the other one of the first wirings as the dummy wiring control voltage during a period in which the one of the first wirings is applied with the first voltage.
8. The semiconductor storage device according to claim 1 , wherein each of the memory cells has a non-ohmic element.
9. The semiconductor storage device according to claim 1 , wherein the control circuit is configured to apply a third voltage higher than the second voltage to others of the second wirings.
10. The semiconductor storage device according to claim 9 , wherein the third voltage is equal to the first voltage.