Magnetoresistive memory cell using floating body effect, memory device having the same, and method of operating the memory device
A magnetoresistive memory cell includes an MTJ device and a select transistor. The select transistor includes a first conduction-type semiconductor layer, a gate electrode formed by disposing a gate insulating layer on top of the semiconductor layer, and first and second diffusion regions formed in the semiconductor layer to be spaced apart from each other and to have a second conduction type. A part of the semiconductor layer between the first and second diffusion regions is formed as an electrically floating body region. By using a high-performance select transistor with a floating body effect, high integration of a magnetoresistive memory device may be achieved.
1. A magnetoresistive memory cell, comprising:
a Magnetic Tunnel Junction (MTJ) device; and
a select transistor, wherein the select transistor comprises:
a first conduction-type semiconductor layer;
a gate electrode formed by disposing a gate insulating layer on top of the semiconductor layer; and
first and second diffusion regions formed in the semiconductor layer to be spaced apart from each other and to have a second conduction type, wherein a part of the semiconductor layer between the first and second diffusion regions is formed as an electrically floating body region and wherein the select transistor comprises a Metal Oxide Semiconductor (MOS) transistor including the gate electrode, the first and second diffusion regions, and the body region and further comprises a Bipolar Junction Transistor (BJT) including the first and second diffusion regions and the body region.
2. The magnetoresistive memory cell according to claim 1 , wherein the MTJ device comprises a free magnetic layer, a tunnel burrier layer and a pinned magnetic layer.
3. The magnetoresistive memory cell according to claim 1 , wherein:
the select transistor is formed on a Substrate-On-Insulator (SOI) semiconductor substrate including the semiconductor layer, a buried oxide, and a base substrate; and
the body region is electrically isolated by the first and second diffusion regions, the gate insulating layer and the buried oxide.
4. A magnetoresistive memory device, comprising:
a memory cell including a Magnetic Tunnel Junction (MTJ) device, and a select transistor including a first conduction-type semiconductor layer, a gate electrode formed by disposing a gate insulating layer on top of the semiconductor layer, first and second diffusion regions formed in the semiconductor layer to be spaced apart from each other and to have a second conduction type, wherein a part of the semiconductor layer between the first and second diffusion regions is formed as an electrically floating body region and wherein the select transistor comprises a Metal Oxide Semiconductor (MOS) transistor including the gate electrode, the first and second diffusion regions, and the body region and further comprises a Bipolar Junction Transistor (BJT) including the first and second diffusion regions and the body region;
a word line electrically connected to the gate electrode;
a bit line electrically connected to one of the first and second diffusion regions through the MTJ device; and
a source line electrically connected to a remaining one of the first and second diffusion regions.
5. The magnetoresistive memory device according to claim 4 , wherein the MTJ device comprises a free magnetic layer, a tunnel burrier layer and a pinned magnetic layer.
6. The magnetoresistive memory device according to claim 4 , wherein:
the select transistor is formed on a Substrate-On-Insulator (S 01 ) semiconductor substrate including the semiconductor layer, a buried oxide, and a base substrate; and
the body region is electrically isolated by the first and second diffusion regions, the gate insulating layer and the buried oxide.
7. A method of operating the magnetoresistive memory device according to claim 4 , comprising:
turning on the MOS transistor including the gate electrode, the first and second diffusion regions and the body region; and
operating the BJT including the first and second diffusion regions and the body region,
wherein a data write mode or read mode is executed by operating the BJT after the MOS transistor has been turned on.
8. The method according to claim 7 , wherein the data write mode of the magnetoresistive memory device is executed by applying a first turn-on voltage of the MOS transistor to the word line, and applying an operating voltage of the BJT between the bit line and the source line.
9. The method according to claim 8 , wherein the first turn-on voltage applied to the word line in the data write mode falls down, after being maintained at a voltage level, for a predetermined delay time from a time point at which the operating voltage of the BJT, applied between the bit line and the source line, has fallen down.
10. The method according to claim 9 , wherein the delay time falls within a range from 0.1 to 10 nanoseconds.
11. The method according to claim 7 , wherein the data read mode of the magnetoresistive memory device is executed by applying a second turn-on voltage of the MOS transistor to the word line and applying an operating voltage of the BJT between the bit line and the source line.
12. The method according to claim 11 , wherein the second turn-on voltage applied to the word line in the data read mode falls down after being maintained at a voltage level, for a predetermined delay time, from a time point at which the operating voltage of the BJT, applied between the bit line and the source line, has fallen down.
13. The method according to claim 12 , wherein the delay time falls within a range from 0.1 to 10 nanoseconds.
14. The method according to claim 8 , wherein the data read mode of the magnetoresistive memory device is executed by applying a second turn-on voltage lower than the first turn-on voltage of the MOS transistor to the word line, and applying the operating voltage of the BJT between the bit line and the source.
15. A magnetoresistive memory device comprising:
a memory cell including a Magnetic Tunnel Junction (MTJ) device; and
a select transistor including a Metal Oxide Semiconductor (MOS) transistor and a Bipolar Junction Transistor (BJT) that are connected in parallel, wherein the MOS transistor and the BJT are connected in common to the MTJ device, are configured to supply current to the MTJ device in response to a gate voltage applied to the gate electrode of the select transistor, and share a common floating body region between a source region and a drain region of the select transistor.
16. The magnetoresistive memory device of claim 15 , wherein:
the select transistor is formed on a Substrate-On-Insulator (SOI) semiconductor substrate including the floating body region, a buried oxide, and a base substrate; and
the body region is electrically isolated by the first and second diffusion regions, a gate insulating layer and the buried oxide.
17. The magnetoresistive memory device of claim 15 , wherein:
the MOS transistor includes the gate electrode, the first and second diffusion regions, and the body region; and
the BJT includes the first and second diffusion regions and the body region.