Memory device incorporating selector element with multiple thresholds
The present invention is directed to a memory device including a memory cell coupled to two wiring lines at two ends thereof. The memory cell includes a memory element, which includes a magnetic free layer and a magnetic reference layer with a tunnel junction layer interposed therebetween, and a bi-directional two-terminal selector element having multiple threshold voltages coupled to the memory element in series. The magnetic free layer has a variable magnetization direction substantially perpendicular to a layer plane thereof and the magnetic reference layer has a fixed magnetization direction substantially perpendicular to a layer plane thereof. In an embodiment, the bi-directional two-terminal selector element includes two selector devices with each selector device including two electrodes with a switching layer interposed therebetween. In another embodiment, the bi-directional two-terminal selector element includes a selector device incorporating therein two switching layers.
1. A memory device comprising a memory cell coupled to two wiring lines at two ends thereof, said memory cell comprising:
a memory element including a magnetic free layer and a magnetic reference layer with a tunnel junction layer interposed therebetween; and
a bi-directional two-terminal selector element coupled to said memory element in series, said bi-directional two-terminal selector element including two selector devices having different threshold voltages coupled in series.
2. The memory device of claim 1 , wherein said magnetic free layer has a variable magnetization direction substantially perpendicular to a layer plane thereof and said magnetic reference layer has a fixed magnetization direction substantially perpendicular to a layer plane thereof.
3. The memory device of claim 1 , wherein each of said two selector devices includes two electrode layers with a switching layer interposed therebetween.
4. The memory device of claim 3 , wherein said two electrode layers are made of a same material.
5. The memory device of claim 3 , wherein said two electrode layers are made of different materials.
6. The memory device of claim 3 , wherein said switching layers of said two selector devices have different compositions.
7. The memory device of claim 3 , wherein said switching layers of said two selector devices have a same composition but different thicknesses.
8. The memory device of claim 3 , wherein at least one of said switching layers of said two selector devices comprises a chalcogenide or oxide.
9. A memory device comprising a memory cell coupled to two wiring lines at two ends thereof, said memory cell including:
a memory element including a magnetic free layer and a magnetic reference layer with a tunnel junction layer interposed therebetween; and
a bi-directional two-terminal selector element coupled to said memory element in series, said bi-directional two-terminal selector element including at least two switching layers having different threshold voltages and a plurality of electrodes separated by said at least two switching layers.
10. The memory device of claim 9 , wherein said magnetic free layer has a variable magnetization direction substantially perpendicular to a layer plane thereof and said magnetic reference layer has a fixed magnetization direction substantially perpendicular to a layer plane thereof.
11. The memory device of claim 9 , wherein said at least two switching layers have different compositions.
12. The memory device of claim 9 , wherein said at least two switching layers have a same composition but different thicknesses.
13. The memory device of claim 9 , wherein at least one of said at least two switching layers comprises a chalcogenide or oxide.
14. The memory device of claim 9 , wherein said plurality of electrodes have a same composition.
15. The memory device of claim 9 , wherein said plurality of electrodes have different compositions.