MAGNETO RESISTIVE ELEMENT AND MAGNETIC MEMORY

A magneto resistive element includes a laminate that includes a first ferromagnetic layer, a second ferromagnetic layer, and a non-magnetic layer located between the first ferromagnetic layer and the second ferromagnetic layer; a first conductive layer that is connected to a first surface of the laminate in a lamination direction; and a second conductive layer that is connected to a second surface opposite the first surface. The first surface of the laminate includes a first region which comes into contact with the first conductive layer and a second region which does not come into contact with the first conductive layer.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a magneto resistive element and a magnetic memory.

Description of Related Art

Magneto resistive elements are elements of which a resistance value in a lamination direction changes due to a magnetic resistance effect. A magneto resistive element includes two ferromagnetic layers and a non-magnetic layer sandwiched therebetween. A magneto resistive element in which a conductor is used as a non-magnetic layer is referred to as a giant magneto resistive (GMR) element, and a magneto resistive element in which an insulating layer (a tunnel barrier layer or a barrier layer) is used as a non-magnetic layer is referred to as a tunnel magneto resistive (TMR) element. Magneto resistive elements can be applied for various purposes, such as magnetic sensors, high-frequency components, magnetic heads, and nonvolatile random access memories (MRAM).

There are several methods for writing data in a magneto resistive element. For example, a method for performing writing utilizing a spin-transfer torque (STT) as disclosed in Japanese Unexamined Patent Application, First Publication No. 2021-103771, and a method for performing writing utilizing a spin-orbit torque (SOT) as disclosed in United States Patent Application, Publication No. 2014/0264513 are known. In a writing method utilizing an STT, a writing current flows in a lamination direction of a laminate including two ferromagnetic layers sandwiching a non-magnetic layer therebetween. In a writing method utilizing an SOT, a writing current flows in a direction intersecting the lamination direction of a laminate including two ferromagnetic layers sandwiching a non-magnetic layer therebetween.

SUMMARY OF THE INVENTION

A magneto resistive element according to a first aspect includes a laminate that includes a first ferromagnetic layer, a second ferromagnetic layer, and a non-magnetic layer located between the first ferromagnetic layer and the second ferromagnetic layer; a first conductive layer that is connected to a first surface of the laminate in a lamination direction; and a second conductive layer that is connected to a second surface opposite the first surface. The first surface of the laminate includes a first region which comes into contact with the first conductive layer and a second region which does not come into contact with the first conductive layer.

DETAILED DESCRIPTION OF THE INVENTION

When writing is performed utilizing an STT, a non-magnetic layer may be damaged due to a writing current flowing in a lamination direction of a laminate. If a non-magnetic layer is damaged, the life span of a magneto resistive element is shortened so that the reliability thereof is degraded. In order to reduce damage to a non-magnetic layer, there is a demand for a magneto resistive element in which writing is facilitated. A magneto resistive element and a magnetic memory according to the present embodiment have excellent writing efficiency.

Hereinafter, the present embodiment will be described in detail suitably with reference to the drawings. In the drawings used in the following description, in order to make characteristics of the present embodiment easy to understand, characteristic parts may be illustrated in an enlarged manner for the sake of convenience, and dimensional ratios or the like of each constituent element may differ from actual values thereof. Materials, dimensions, and the like exemplified in the following description are examples. The present invention is not limited thereto and can be changed and performed within a range not changing the gist thereof suitably.

First, directions will be defined. The lamination direction of a laminate10(which will be described below) will be referred to as a z direction. A direction orthogonal to the z direction will be referred to as an x direction, and a direction orthogonal to the x direction and the z direction will be referred to as a y direction. The z direction is an example of the lamination direction. A direction from a first conductive layer20toward a second conductive layer30will be referred to as a positive z direction. Hereinafter, the positive z direction may be expressed as “upward”, and a negative z direction may be expressed as “downward”. The upward and downward directions do not necessarily coincide with a direction in which gravity is applied.

First Embodiment

FIG.1is a circuit diagram of a magnetic memory200according to a first embodiment. The magnetic memory200includes a plurality of magneto resistive elements100, a plurality of source lines SL, a plurality of bit lines BL, a plurality of first switching elements Sw1, and a plurality of second switching elements Sw2.

For example, the plurality of magneto resistive elements100are arrayed in a matrix shape. Each magneto resistive element100is connected to the source line SL and the bit line BL.

The source line SL electrically connects the first switching element Sw1and the magneto resistive element100to each other. The bit line BL electrically connects the second switching element Sw2and the magneto resistive element100to each other.

When a predetermined first switching element Sw1and a predetermined second switching element Sw2are turned on, a current flows in a predetermined magneto resistive element100. A current also flows in the lamination direction of the magneto resistive element100at the time of wiring and reading data. A writing current is greater than a reading current. A writing current causes a spin-transfer torque to act on magnetization of the magneto resistive element100such that data is written in the magneto resistive element100. The magneto resistive element100is a two-terminal-type element operating with two switching elements.

The first switching element Sw1and the second switching element Sw2are elements controlling a flow of a current. For example, the first switching element Sw1and the second switching element Sw2are transistors, elements utilizing phase change of a crystal layer, such as ovonic threshold switches (OTS); elements utilizing change of a band structure, such as metal-insulator transition (MIT) switches; elements utilizing a breakdown voltage, such as Zener diodes or avalanche diodes; or elements of which conductivity changes in accordance with change in position of atoms.

FIG.2is a perspective view of the magneto resistive element100according to the first embodiment. The magneto resistive element100has the laminate10, the first conductive layer20, and the second conductive layer30. Each of the laminate10, the first conductive layer20, and the second conductive layer30is a columnar body.

An area of the magneto resistive element100is covered by an insulating layer (not illustrated). The insulating layer is an insulating layer insulating wirings or elements of a multilayer wiring. For example, the insulating layer is made of silicon oxide (SiOx), silicon nitride (SiNx), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrOx), or the like.

The first conductive layer20is connected to a first surface11of the laminate10. The second conductive layer30is connected to a second surface12of the laminate10. The first surface11and the second surface12are two surfaces at both ends of the laminate10in the z direction, and they face each other. The first conductive layer20and the second conductive layer30are made of a conductive material. The first conductive layer20and the second conductive layer30are also referred to as via wirings. For example, the first conductive layer20and the second conductive layer30include any one selected from the group consisting of Al, Cu, Ta, Ti, Zr, NiCr, and nitrides (for example, TiN, TaN, and SiN).

For example, the laminate10includes a first ferromagnetic layer1, a second ferromagnetic layer2, a non-magnetic layer3, a base layer4, and a cap layer5.

A resistance value of the laminate10changes when a relative angle between a magnetization of the first ferromagnetic layer1and a magnetization of the second ferromagnetic layer2changes. The magneto resistive element100stores data on the basis of the resistance value of the laminate10. For example, a case in which the magnetization of the first ferromagnetic layer1and the magnetization of the second ferromagnetic layer2are parallel to each other will be referred to as “0”, and a case in which the magnetization of the first ferromagnetic layer1and the magnetization of the second ferromagnetic layer2are antiparallel to each other will be referred to as “1”.

Each of the first ferromagnetic layer1and the second ferromagnetic layer2has a magnetization. For example, in the magnetization of the first ferromagnetic layer1, an orientation direction is less likely to change than that in the magnetization of the second ferromagnetic layer2when a predetermined external force is applied. In this case, the first ferromagnetic layer1is referred to as a magnetization fixed layer, and the second ferromagnetic layer2is referred to as a magnetization free layer or a magnetization reference layer. In order to enhance stability of the magnetization, the first ferromagnetic layer1may be on a substrate side which is the base rather than the second ferromagnetic layer2. A case in which the first ferromagnetic layer1is a magnetization fixed layer and the second ferromagnetic layer2is a magnetization free layer has been described as an example, but the first ferromagnetic layer1may be a magnetization free layer and the second ferromagnetic layer2may be a magnetization fixed layer.

The first ferromagnetic layer1and the second ferromagnetic layer2include a ferromagnetic body. For example, a ferromagnetic body is a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy including one or more kinds of these metals, an alloy including at least one or more kinds of elements of these metals, B, C, and N, or the like. For example, a ferromagnetic body is a Co—Fe, a Co—Fe—B, a Ni—Fe, a Co—Ho alloy, a Sm—Fe alloy, a Fe—Pt alloy, a Co—Pt alloy, or a CoCrPt alloy.

The first ferromagnetic layer1and the second ferromagnetic layer2may include a Heusler alloy. A Heusler alloy includes an intermetallic compound having a chemical composition of XYZ or X2YZ. X is a transition metal element or a noble metal element of the Co group, the Fe group, the Ni group, or the Cu group in the periodic table, Y is a transition metal of the Mn group, the V group, the Cr group, or the Ti group or a kind of element as for X, and Z is a typical element from Group III to Group V. For example, a Heusler alloy is Co2FeSi, Co2FeGe, Co2FeGa, Co2MnSi, Co2Mn1-aFeaAlbSi1-bh, Co2FeGe1-cGac, or the like. A Heusler alloy has a high spin polarization coefficient.

The first ferromagnetic layer1and the second ferromagnetic layer2may be constituted of a plurality of layers. The first ferromagnetic layer1and the second ferromagnetic layer2may be a synthetic antiferromagnetic structure (SAF structure). A synthetic antiferromagnetic structure is constituted of two magnetic layers sandwiching a spacer layer therebetween. A coercive force of a magnetic body increases by coupling two ferromagnetic layers sandwiching a spacer layer therebetween. For example, a spacer layer is made of Ru, Ir, Ta, Rh, or the like.

The non-magnetic layer3is sandwiched between the first ferromagnetic layer1and the second ferromagnetic layer2in the z direction.

The non-magnetic layer3includes a non-magnetic body. When the non-magnetic layer3is an insulator (when it is a tunnel barrier layer), for example, Al2O3, SiO2, MgO, MgAl2O4, or the like can be used as a material thereof. Furthermore, in addition to these, a material in which a portion of Al, Si, or Mg is substituted with Zn, Be, or the like, or the like can be used. Among these, since MgO or MgAl2O4is a material which can realize a coherent tunnel, spins can be efficiently injected. When the non-magnetic layer3is made of a metal, Cu, Au, Ag, or the like can be used as a material thereof. Moreover, when the non-magnetic layer3is a semiconductor, Si, Ge, CuInSe2, CuGaSe2, Cu(In,Ga) See, or the like can be used as a material thereof.

The base layer4is on the substrate side supporting the laminate10. For example, the base layer4is located between the first conductive layer20and the first ferromagnetic layer1. For example, the base layer4is a seed layer or a buffer layer. A seed layer enhances crystallinity of a layer laminated on the seed layer. For example, a seed layer is made of Pt, Ru, Hf, Zr, or NiFeCr. A buffer layer is a layer alleviating lattice mismatch between different crystals. For example, a buffer layer is made of Ta, Ti, W, Zr, Hf, or nitride of these elements.

The cap layer5is on a side away from a substrate of the laminate10. For example, the cap layer5is located between the second conductive layer30and the second ferromagnetic layer2. The cap layer5prevents damage to an underlayer during a process and enhances crystallinity of an underlayer at the time of annealing. For example, the cap layer5is made of MgO, W, Mo, Ru, Ta, Cu, or Cr or is constituted of a laminated film or the like.

The laminate10may have a layer other than the first ferromagnetic layer1, the second ferromagnetic layer2, the non-magnetic layer3, the base layer4, and the cap layer5. In addition, the laminate10may not have the base layer4and the cap layer5.

FIG.3is a cross-sectional view of the magneto resistive element100according to the first embodiment.FIG.3is an xz-cross section passing through a geometrical center of the magneto resistive element100.

A portion of the laminate10comes into contact with the first conductive layer20. The first surface11of the laminate10has a first region13which comes into contact with the first conductive layer20, and a second region14which does not come into contact with the first conductive layer20. In addition, for example, a portion of the laminate10comes into contact with the second conductive layer30. The second surface12of the laminate10has a third region15which comes into contact with the second conductive layer30, and a fourth region16which does not come into contact with the second conductive layer30.

For example, a first surface21of the first conductive layer20has a first region22which comes into contact with the laminate10, and a second region23which does not come into contact with the laminate10. The first surface21is a surface of the first conductive layer20on the laminate10side.

For example, a first surface31of the second conductive layer30has a first region32which comes into contact with the laminate10, and a second region33which does not come into contact with the laminate10. The first surface31is a surface of the second conductive layer30on the laminate10side.

FIG.4is a plan view of the magneto resistive element100according to the first embodiment.

When viewed in the z direction, the shapes of the laminate10, the first conductive layer20, and the second conductive layer30are circular shapes, for example. The shapes thereof in a plan view are not limited to circular shapes. For example, the shapes thereof in a plan view are elliptical shapes, oval shapes, quadrangular shapes, or the like.

For example, a geometrical center C10of the laminate10is misaligned with a geometrical center C20of the first conductive layer20. For example, the geometrical center C10of the laminate10is misaligned with a geometrical center C30of the second conductive layer30. For example, the geometrical center C20of the first conductive layer20is misaligned with the geometrical center C30of the second conductive layer30.

InFIG.4, the geometrical center C20is located at a position overlapping the laminate10in the z direction, but the geometrical center C20may be located on the outward side of the laminate10when viewed in the z direction. Similarly, the geometrical center C30may be located on the outward side of the laminate10when viewed in the z direction. In addition, the geometrical center C10may be located on the outward side of the first conductive layer20and the second conductive layer30when viewed in the z direction.

InFIG.4, the geometrical center C20and the geometrical center C30are misaligned with the geometrical center C10in the x direction. A misalignment direction of the geometrical center C20and the geometrical center C30with respect to the geometrical center C10is not limited to this example, and it does not matter particularly. In addition, the geometrical center C10, the geometrical center C20, and the geometrical center C30are not necessarily arranged on the same line. For example, as in a magneto resistive element100A illustrated inFIG.5, a segment connecting the geometrical center C10and the geometrical center C20to each other may intersect a segment connecting the geometrical center C10and the geometrical center C30to each other.

When viewed in the z direction, the first conductive layer20and the second conductive layer30may have parts overlapping each other (which will hereinafter be referred to as an overlapping part40). A writing current is maximally concentrated in the overlapping part40. Magnetization reversal of the second ferromagnetic layer2in its entirety is triggered when the magnetization of the overlapping part40is reversed.

A circumferential length of each of the laminate10, the first conductive layer20, and the second conductive layer30does not matter particularly. For example, the circumferential length of the first conductive layer20is shorter than the circumferential length of the laminate10. In the cross section illustrated inFIG.3, a width of the first conductive layer20in the x direction is shorter than a width of the laminate10in the x direction. For example, the circumferential length of the second conductive layer30is shorter than the circumferential length of the laminate10. In the cross section illustrated inFIG.3, a width of the second conductive layer30in the x direction is shorter than the width of the laminate10in the x direction. A surface area of a part in which the laminate10comes into contact with the first conductive layer20or the second conductive layer30can be narrowed by making the circumferential length of the first conductive layer20or the second conductive layer30shorter than the circumferential length (width) of the laminate10. When a writing current is concentrated and flows in this part inside the laminate10, the magnetization of the second ferromagnetic layer2is likely to be reversed.

The magneto resistive element100according to the first embodiment can be produced by repeating a laminating step and a processing step for each layer.

For example, the first conductive layer20can be produced by forming an opening in an insulating layer and filling the inside with a conductor.

The laminate10can be produced by flattening surfaces of the first conductive layer20and an insulating layer, laminating each of the layers thereafter, and processing the layers into predetermined shapes. For example, processing of the laminate10is performed by photolithography or the like. An area around the laminate10is covered by the insulating layer.

The second conductive layer30can be produced by flattening surfaces of the laminate10and an insulating layer, laminating the insulating layer thereafter, forming an opening in the insulating layer, and filling the inside with a conductor.

In the magneto resistive element100according to the first embodiment, the magnetization of the second ferromagnetic layer2can be reversed even with a small current. That is, the magneto resistive element100according to the first embodiment has a small inversion current density and high writing efficiency.

FIG.6is a schematic view for describing effects of the magneto resistive element100according to the first embodiment.

When data is written in the magneto resistive element100, a writing current is applied thereto in the z direction of the laminate10. Inside the laminate10, a writing current is concentrated in a first part41connecting the first region13in which the laminate10and the first conductive layer20come into contact with each other to the third region15in which the laminate10and the second conductive layer30come into contact with each other. In addition, a writing current is particularly concentrated in the overlapping part40inside the laminate10.

The magnetization of the second ferromagnetic layer2is reversed when the current density of a writing current exceeds a predetermined value. When a writing current is concentrated in the first part41, the current density of the first part41increases. When the current density of the first part41exceeds a predetermined value, the magnetization of the second ferromagnetic layer2in the first part41is reversed. When the magnetization of the second ferromagnetic layer2in the first part41is reversed, in order to retain magnetic stability, the magnetization of a part other than the first part41in the second ferromagnetic layer2is also reversed. That is, when there is a part in which a writing current is concentrated inside the laminate10, magnetization reversal of this part becomes a trigger so that the magnetization of other parts is also easily reversed.

A current density of a writing current is a value obtained by dividing a current amount of a writing current by a surface area in which a current flows. When a writing current is concentrated in the first part41, the surface area in which a current flows (denominator) is reduced. Therefore, even when the current amount of a writing current is small, the current density of the first part41can have a predetermined value or larger. Namely, in the magneto resistive element100according to the first embodiment, the magnetization of the second ferromagnetic layer2can be reversed with a small amount of writing current, and high writing efficiency is achieved.

In addition, as described above, a writing current is more likely to be concentrated in the overlapping part40than any part in the first part41. Therefore, when the magneto resistive element100has the overlapping part40, writing efficiency of the magneto resistive element100can be further enhanced.

In addition, in the laminate10, a writing current flows in a direction inclined with respect to the z direction. That is, a writing current has a component in any direction within an xy plane (which will hereinafter be referred to as an in-plane component). The in-plane component of a writing current applies a spin-orbit torque (SOT) to the magnetization of the second ferromagnetic layer2. That is, when a writing current has an in-plane component, a spin-orbit torque (SOT) is applied to the magnetization of the second ferromagnetic layer2in addition to a spin-transfer torque (STT). Since a spin-orbit torque (SOT) additionally acts on the magnetization thereof, the magneto resistive element100has high writing efficiency.

Second Embodiment

FIG.7is a cross-sectional view of a magneto resistive element101according to a second embodiment.FIG.7illustrates a cross section which passes through a geometrical center of a first conductive layer20A and the geometrical center of the laminate10viewed in the z direction and is cut in the z direction. In the magneto resistive element101according to the second embodiment, the same reference signs are applied to constituents similar to those of the magneto resistive element100according to the first embodiment, and description thereof will be omitted.

The magneto resistive element101has the first conductive layer20A, the laminate10, and a second conductive layer30A.

The first conductive layer20A differs from the first conductive layer20in that the entire first surface21comes into contact with the laminate10. In addition, the second surface12of the laminate10comes into contact with the second conductive layer30A on the entire surface thereof. The second conductive layer30A has a longer circumferential length than the circumferential length of the laminate10. As illustrated inFIG.7, a side surface20As of the first conductive layer20A and a side surface10sof the laminate10may be continuously formed. Here, continuously formed side surfaces denote that there is no step between boundary surfaces of different layers. For example, when a cross section is confirmed at a magnification at which the laminate10in its entirety can be confirmed, if inclinations of tangential lines of two side surfaces continuously change or are uniform, it can be said that the two side surfaces are continuously formed.

The magneto resistive element101according to the second embodiment has a first part41A in which a writing current is concentrated, and a writing current flowing in the first part41A has an in-plane component. Therefore, effects similar to those of the magneto resistive element100can be obtained.

Third Embodiment

FIG.8is a cross-sectional view of a magneto resistive element102according to a third embodiment. In the magneto resistive element102according to the third embodiment, the same reference signs are applied to constituents similar to those of the magneto resistive element100according to the first embodiment, and description thereof will be omitted.

In the magneto resistive element102, the shape of a second conductive layer30B differs from that in the magneto resistive element100. In the magneto resistive element102, the surface area of the third region15is narrower than the surface area of the first region13. For this reason, a cross-sectional area of a first part41B in which a writing current is concentrated becomes smaller as it goes closer to the second conductive layer30B. The current density of the second ferromagnetic layer2is higher than the current density of the first ferromagnetic layer1.

The first ferromagnetic layer1is a magnetization fixed layer. When the magnetization of the first ferromagnetic layer1is reversed, a reference to the resistance value fluctuates so that reliability of data of the magneto resistive element102is degraded. Unexpected magnetization reversal of the magnetization of the first ferromagnetic layer1is curbed by increasing the cross-sectional area of the first part41B in the first ferromagnetic layer1and decreasing the current density at the time of passing through the first ferromagnetic layer1.

The magneto resistive element102according to the third embodiment has the first part41B in which a writing current is concentrated, and a writing current flowing in the first part41B has an in-plane component. Therefore, effects similar to those of the magneto resistive element100can be obtained. In addition, in the magneto resistive element102according to the third embodiment, unexpected magnetization reversal of the magnetization of the first ferromagnetic layer1is curbed, and excellent reliability is achieved.

Fourth Embodiment

FIG.9is a cross-sectional view of a magneto resistive element103according to a fourth embodiment. In the magneto resistive element103according to the fourth embodiment, the same reference signs are applied to constituents similar to those of the magneto resistive element100according to the first embodiment, and description thereof will be omitted.

The magneto resistive element103has the laminate10, the first conductive layer20, and a second conductive layer30C. A geometrical center of the second conductive layer30C is on the same side as the geometrical center of the first conductive layer20with respect to the geometrical center of the laminate10in the x direction.

The magneto resistive element103according to the fourth embodiment has a first part41C in which a writing current is concentrated. Therefore, effects similar to those of the magneto resistive element100can be obtained.

Fifth Embodiment

FIG.10is a cross-sectional view of a magneto resistive element104according to a fifth embodiment. In the magneto resistive element104according to the fifth embodiment, the same reference signs are applied to constituents similar to those of the magneto resistive element100according to the first embodiment, and description thereof will be omitted.

The magneto resistive element104has the laminate10, a first conductive layer20D, and a second conductive layer30D.

The first conductive layer20D differs from the first conductive layer20in that it comes into contact with a portion of a side wall of the laminate10. The first conductive layer20D comes into contact with a side wall of the first ferromagnetic layer1or the base layer4.

The second conductive layer30D differs from the second conductive layer30in that it comes into contact with a portion of the side wall of the laminate10. The second conductive layer30D comes into contact with a side wall of the second ferromagnetic layer2or the cap layer5.

InFIG.10, an example in which both the first conductive layer20D and the second conductive layer30D come into contact with the side wall of the laminate10has been described, but only one may come into contact therewith.

The magneto resistive element104according to the fifth embodiment has a first part41D in which a writing current is concentrated, and a writing current flowing in the first part41D has an in-plane component. Therefore, effects similar to those of the magneto resistive element100can be obtained. In addition, in the magneto resistive element104according to the fifth embodiment, the first conductive layer20D or the second conductive layer30D comes into contact with the side wall of the laminate10. Therefore, a contact resistance between boundary surfaces thereof decreases. When the boundary surface resistance decreases, a specific resistance of the magneto resistive element104which is an unchanging resistance decreases. Therefore, a magnetic resistance change rate of the magneto resistive element104increases.

Sixth Embodiment

FIG.11is a cross-sectional view of a magneto resistive element105according to a sixth embodiment.FIG.11illustrates a cross section which passes through a geometrical center of a first conductive layer20E and a geometrical center of a laminate10E viewed in the z direction and is cut in the z direction. In the magneto resistive element105according to the sixth embodiment, the same reference signs are applied to constituents similar to those of the magneto resistive element100according to the first embodiment, and description thereof will be omitted.

The magneto resistive element105has the laminate10E, the first conductive layer20E, and a second conductive layer30E. The constitution of each of the laminate10E, the first conductive layer20E, and the second conductive layer30E is substantially the same as the laminate10, the first conductive layer20, and the second conductive layer30according to the first embodiment. Hereinafter, regarding the laminate10E, the first conductive layer20E, and the second conductive layer30E, parts different from the laminate10, the first conductive layer20, and the second conductive layer30according to the first embodiment will be described in detail.

A side surface10Es of the laminate10E is inclined with respect to the z direction. In addition, the laminate10E has a vertical magnetic induction layer6. The vertical magnetic induction layer6comes into contact with an upper surface of the second ferromagnetic layer2. For example, the vertical magnetic induction layer6enhances vertical magnetic anisotropy of the second ferromagnetic layer2. For example, the vertical magnetic induction layer6is made of magnesium oxide, W, Ta, Mo, or the like. When the vertical magnetic induction layer6is made of magnesium oxide, it is preferable that the magnesium oxide is oxygen-deficient in order to enhance conductivity. For example, a film thickness of the vertical magnetic induction layer6is 0.5 nm to 5.0 nm. Since the laminate10has the vertical magnetic induction layer6, an MR ratio of the magneto resistive element105can be enhanced.

The first conductive layer20E is connected to the first surface11of the laminate10E. The first conductive layer20E comes into contact with a portion of the first surface11. The first conductive layer20E has a first columnar portion20E1and a second columnar portion20E2. The first columnar portion20E1comes into contact with the laminate10E. The second columnar portion20E2comes into contact with the first columnar portion20E1. In the z direction, the first columnar portion20E1is sandwiched between the second columnar portion20E2and the laminate10E.

A circumferential length of the first columnar portion20E1becomes longer moving away from the laminate10E. A cross-sectional area of the first columnar portion20E1increases moving away from the laminate10E. A circumferential length of the second columnar portion20E2becomes shorter moving away from the laminate10E. A cross-sectional area of the second columnar portion20E2is narrowed moving away from the laminate10E.

As illustrated inFIG.11, for example, a side surface20E1sof the first columnar portion20E1and the side surface10Es of the laminate10E are continuously formed. When the side surface20E1sand the side surface10Es are continuously formed, a current smoothly flows on this boundary surface. That is, occurrence of local concentration of a current on a boundary surface between the first conductive layer20E and the laminate10E can be curbed. Local concentration of a current may cause heat generation or the like, which may cause a malfunction of the magneto resistive element105.

For example, the first conductive layer20E is produced in the following procedure. First, an opening is formed in an insulating layer, and the inside thereof is filled with a conductor. Further, layers which will serve as the laminate10E are laminated on the insulating layer and the conductor filling the inside of the opening. Next, when the side surface10Es of the laminate10E is formed, an upper portion of the conductor filling the inside of the opening is simultaneously etched. At this time, the side surface20E1sis formed, and the first columnar portion20E1is formed. In the conductor filling the inside of the opening, a part which is not etched becomes the second columnar portion20E2. For example, the side surface20E1sis simultaneously formed at the time of processing when the side surface10Es of the laminate10E is formed.

The second conductive layer30E is connected to the second surface12of the laminate10E. The second conductive layer30E comes into contact with a portion of the second surface12. For example, the third region15which comes into contact with the second conductive layer30is positioned below the fourth region16which does not come into contact with the second conductive layer30. A writing current can be concentrated in a region connecting the first conductive layer20E and the second conductive layer30E to each other by satisfying the constitution.

A circumferential length of the second conductive layer30E becomes longer moving away from the laminate10E. A cross-sectional area of the second conductive layer30E increases moving away from the laminate10E. The second conductive layer30E comes into contact with a portion of a side wall10Es of the laminate10E. For example, the second conductive layer30E comes into contact with the side wall of the cap layer5.

The magneto resistive element105according to the sixth embodiment has a first part41E in which a writing current is concentrated. Therefore, effects similar to those of the magneto resistive element100can be obtained. In addition, in the magneto resistive element105according to the sixth embodiment, the side surface10Es of the laminate10E and the side surface20E1sof the first conductive layer20E are continuously formed. Therefore, local concentration of a current can be avoided. In addition, since the first conductive layer20E has a two-stage structure, a flow of a current can be made smoother.

Hereinabove, the embodiments of the present invention have been described in detail with reference to the drawings. However, the constituents and combinations thereof in each of the embodiments are examples, and the constituents can be subjected to addition, omission, replacement, and other changes within a range not departing from the gist of the present invention. In addition, characteristic constituents in each of the embodiments may be combined.

EXPLANATION OF REFERENCES