In recent years, attempts have been actively performed for applying a magnetoresistive effect device utilizing a tunnel magnetoresistive effect to magnetic random access memory as a memory device. The magnetic random access memory using the magnetoresistive effect device has a feature in which data can be stored in a non-volatile manner, and the write/read time is 10 ns or less, and the number of times of rewriting is 1015 or more.
Writing to the magnetoresistive effect device is performed by a spin transfer torque magnetization switching method in general, and magnetization of a magnetic storage layer is switched by injecting spin-polarized electrons (spin injection current) into the magnetic storage layer of the memory device. Since an amount of the current required for writing is decreased with miniaturization of the magnetic storage layer, the method is greatly expected as a writing method of the magnetic random access memory.
However, since magnetization writing by the spin transfer torque magnetization switching is a current writing method in principle, and a large current density is required of about 0.5 MA/cm2 in the present circumstances, problems have occurred such as an increase in power consumption, an increase in a peripheral circuit area, and an increase in a cell selection transistor area.
To solve these problems, in recent years, a voltage magnetization writing method has been known. In the voltage magnetization writing method, by applying a voltage to the magnetic storage layer of the magnetoresistive effect device via an insulating layer, the number of electrons is changed of the magnetic storage layer in the vicinity of an interface with the insulating layer, and a magnetization direction of the magnetic storage layer is changed. When the voltage magnetization writing method is used, the above-described problems in the conventional spin transfer torque magnetization switching method can be solved, and a low power consumption magnetic random access memory can be configured. However, in a case in which the voltage magnetization writing method is used to the normal magnetoresistive effect device, that is, in a case in which the magnetization direction is controlled by applying an electric field to the magnetic storage layer via a tunnel barrier (tunnel insulating layer) of the magnetoresistive effect device, there is a problem that it is necessary to develop a technique for preventing breakdown of the tunnel barrier, and a material for increasing an amount of change of a magnetization state to an applied voltage.
As described above, the voltage writing method magnetic random access memory to which attention has been paid in recent years has advantages in reducing power consumption and increasing a degree of integration, but it is necessary to solve problems, such as suppression of breakdown of the tunnel barrier, and an increase in an amount of modulation of the magnetization state to the applied voltage.
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