MRAM and method of manufacturing the same

A magnetic memory device includes a first write wiring line including a wiring layer formed in a trench in an insulation layer, a barrier metal layer buried in the trench over the wiring layer. And the device includes a magneto-resistance effect element provided on the first write wiring line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-154885, filed May 25, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a magnetic memory device and a method of manufacturing the same, and more particularly to a magnetic random access memory (MRAM) and a method of manufacturing the same.

2. Description of the Related Art In a conventional cross-point type MRAM, for example, an MTJ (Magnetic Tunnel Junction) element is, in many cases, provided at a cross point between a bit line and a word line, and the word line is formed such that a metal such as Cu (copper) is buried in a trench in an insulation layer.

After a wiring layer such as a word line is formed in the trench by means of a damascene method, however, it is necessary to subject the metal to a wet etching process or heating treatment, thereby to enhance insulation properties (see, e.g. U.S. Pat. No. 6,261,953). In the step of wet etching, surface roughness occurs on the metal. In the heating treatment, too, surface roughness occurs on the metal since grain boundaries grow in the metal. If such surface roughness occurs on the metal and the surface of the word line becomes uneven, the cross-sectional shape of the MTJ element that is provided on the word line (WL) tends to be distorted in accordance with the uneven surface of the word line.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a first write wiring line including a wiring layer formed in a trench in an insulation layer, a barrier metal layer buried in the trench over the wiring layer, a surface of the barrier metal layer being flatter than a surface of the wiring layer, and a magneto-resistance effect element provided on the surface of the barrier metal layer.

According to another aspect of the present invention, there is provided a method of manufacturing a magnetic memory device, the method comprising forming a trench in an insulation layer, the trench extending in one direction, forming a first magnetic layer along an inner wall of the trench, forming a metal layer on the first magnetic layer, flattening the magnetic layer and the metal layer and burying the magnetic layer and the metal layer in the trench, thereby forming a first yoke layer and a wiring layer, subjecting a surface of the first yoke layer and a surface of the wiring layer to wet etching, forming a barrier metal layer on the wiring layer that is recessed by the wet etching, flattening the barrier metal layer at a level of the surface of the first yoke layer and burying the barrier metal layer in the trench such that a surface of the barrier metal layer is continuous with the surface of the first yoke layer, and subjecting the wiring layer to heat treatment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described with reference to the accompanying drawings. In the descriptions below, common parts are denoted by like reference numerals throughout the drawings.

A magnetic memory device according to a first embodiment of the present invention and a method of manufacturing the same are described referring toFIG. 1toFIG. 3.FIG. 1is a cross-sectional view that schematically shows the structure of the magnetic memory device according to the first embodiment of the present invention. The magnetic memory device according to this embodiment is described by taking, as an example, a so-called 1T1MTJ (1 Transistor-1 Magnetic Tunnel Junction) type MRAM wherein an MTJ (Magnetic Tunnel Junction) element (magneto-resistance effect element) is electrically connected to one end of the current path of a transistor.

A transistor (select transistor) TR for selecting an MTJ element is provided on a major surface of the semiconductor substrate (Si substrate)31. The MTJ (Magnetic Tunnel Junction) element (magneto-resistance effect element) is provided in an insulation layer45at an intersection between a bit line BL (write line) and a word line WL (write line). An insulation layer46is provided on the bit line BL. A region indicated by a broken line inFIG. 1designates a 1-bit memory cell MC.

The transistor TR comprises a gate electrode33, which is provided on the major surface of the substrate31with a gate insulation film32interposed, and a source S and a drain D, which are provided in the substrate31so as to sandwich the gate electrode33. A source line contact SC is provided on the source S. A source line SL, which applies a common potential to sources S of a plurality of memory cells MC (not shown) that are provided along the word line WL, is provided on the source line contact SC. Drain contacts DC-1to DC-4are provided on the drain D. The drain contacts DC-1to DC4electrically connect the MTJ element and the drain D via an underlying conductive layer40.

The MTJ element is configured, for example, such that a tunneling barrier layer (insulation layer)42is sandwiched between a free layer (ferromagnetic layer)41and a pinned layer (ferromagnetic layer)43. The MTJ element stores “1” data or “0” data in a nonvolatile state, depending on whether the directions of magnetization of the free layer41and pinned layer43are parallel or antiparallel. The stored “1” data or “0” data is read out by making use of a so-called TMR (Tunneling Magneto-Resistance) effect of the magnetic tunnel junction (MTJ). The magnetization direction of the pinned layer43is fixed. The magnetization direction of the free layer41alone is switched between “parallel” and “antiparallel” by a composite field that is produced from the bit line BL and word line WL.

The word line WL comprises a Cu wiring layer (wiring layer)37that is buried in a trench formed in the insulation layer34; a yoke layer36that is provided at an interface between the Cu wiring layer37and the trench; and a barrier metal layer38that is buried in the trench over the Cu wiring layer37. The barrier metal layer38is formed of, e.g. Ta, Ti, TiN, or TaN. The yoke layer36is formed of a ferromagnetic material including a high-permeability magnetic material such as NiFe.

Information in the MTJ element is read out by detecting the resistance value of the MTJ element. When the magnetization direction of the free layer41is parallel to the magnetization direction of the pinned layer43, the resistance value of the MTJ element is minimum, and the MTJ element is set, for example, in a “1” state. On the other hand, when the magnetization direction of the free layer41is antiparallel (i.e. opposite in the direction of the bit line BL) to the magnetization direction of the pinned layer43, the resistance value of the MTJ element is maximum, and the MTJ element is set, for example, in a “0” state. The parallel and antiparallel states, which correspond to the “1” state and “0” state, can be switched by executing a write operation and reversing the magnetization direction of the free layer41.

Specifically, the read operation is executed by causing an electric current to successively flow through the underlying conductive layer40, free layer41, tunneling barrier layer42, pinned layer43and bit line BL. Further, the current is amplified and detected by, e.g. a sense amplifier (not shown) that is connected to the bit line BL. The resistance value is thus detected to complete the read operation.

On the other hand, information is written in the MTJ element by reversing the magnetization direction of the free layer41by application of a composite magnetic field that is generated by the word line WL and bit line BL. To start with, a current is let to flow in the word line WL. As a result, a magnetic field is generated around the word line WL according to so-called Ampere's rule. Similarly, a current is let to flow in the bit line BL, thereby generating a magnetic field around the bit line BL. The composite magnetic field that is generated by the word line WL and bit line BL reverses only the magnetization direction of the free layer41of the MTJ element. Thus, data can be written only in an MTJ element of a plurality of arrayed MTJ elements, which is provided at an intersection between a selected word line WL and a selected bit line BL.

The word line WL includes the yoke layer36that contains a high-permeability magnetic material and is formed at the interface between the Cu wiring layer and the inside of the trench. Thus, in the write operation, of the magnetic fluxes generated from the word line WL, most of magnetic fluxes that come from the bottom and side surfaces of the word line WL are led to the yoke layer36.

As has been described above, in the magnetic memory device according to this embodiment, the Cu wiring layer (wiring layer)37is buried in the trench that is formed in the insulation layer34, and the barrier metal layer38is buried in the trench over the Cu wiring layer37.

The MTJ element is thus provided on the flattened insulation layer35and underlying conductive layer40such that the MTJ element has a flat cross-sectional shape. Since the magnetic characteristics of the MTJ element can be made uniform, the write current for the MTJ element can be made uniform for each memory cell MC in the write operation, and the reliability can be enhanced at the time of data write in the memory cell MC. In other words, this prevents occurrence of stress, tensile force, etc. in the MTJ element due to distortion in the cross-sectional shape of the MTJ element, and an increase in, e.g. a switching field for reversing magnetization. Moreover, since the cross-sectional shape of the MTJ element is flat, the film thickness, etc. of the MTJ element can be made uniform for each memory cell MC. In short, since the resistance value of the MTJ element can be made uniform for each memory cell MC at the time of the read operation and the read margin of the memory cell MC can be enhanced, the reliability at the time of read from the memory cell MC can be enhanced.

Moreover, since the surfaces of the barrier metal layer38and yoke layer36are formed continuous and flat, the surface of the insulation layer35that is formed on the barrier metal layer38and yoke layer36is also flat. In order to achieve flattening, there is not need to form a thick insulation layer on the Cu wiring layer37, bury the insulation layer in the trench and flatten the insulation layer. It should suffice to form the insulation layer35with such a small thickness as to secure electrical insulation between the word line WL and the MTJ element. It is possible, therefore, to form a thin insulation layer35. As a result, the distance between the MTJ element and word line WL can be reduced, and a write current can be decreased.

Furthermore, the word line WL includes the yoke layer36that contains a high-permeability magnetic material and is formed at the interface between the Cu wiring layer37and the inside of the trench. Thus, in the write operation, most of magnetic fluxes that come from the bottom and side surfaces of the word line WL are led to the yoke layer36. It is possible to prevent the generated magnetic fluxes from extending in random directions, and also to prevent generated magnetic fluxes from interfering with each other, which results in erroneous data write. The above-described yoke layer36can reduce the write current that flows in the word line WL. To be more specific, the provision of the yoke layer36can advantageously achieve, for example, about double the efficiency (i.e. the write current value is reduced to about ½ ).

Referring now toFIG. 2andFIG. 3, a description is given of a method of manufacturing the magnetic memory device according to the first embodiment, taking the magnetic memory device shown inFIG. 1by way of example.

To start with, using well-known fabrication steps, as illustrated inFIG. 2, a transistor TR, drain contacts DC-1to DC-3, a source contact SC, a source line SL and an insulation layer34are formed on a major surface of a semiconductor substrate31. Further, using well-known fabrication steps, a trench39is formed in the insulation layer34, and a magnetic film of, e.g. NiFe, which will serve as a yoke layer36, and a Cu film, which will serve as a Cu wiring layer37, are formed on the entire surface (not illustrated).

Using, e.g. CMP (Chemical Mechanical Polishing), etching is performed down to the surface of the insulation layer34and the structure is flattened at the level of the surface of the insulation layer34. Thus, the magnetic film and Cu film are buried in the trench39.

Subsequently, the entire surface of the resultant structure is subjected to wet etching.

On the entire surface, a Ta film, for instance, which will serve as a barrier metal layer38, is formed using, e.g. CVD (Chemical Vapor Deposition).

The Ta film, as shown inFIG. 3, is polished by, e.g. CMP until the surface of the insulation film34is flattened, and the Ta film is buried in the trench39. Thus, the barrier metal layer38is formed on the Cu wiring layer37.

Then, the Cu wiring layer37is subjected to heat treatment, and grain boundaries of Cu metal in the Cu wiring layer37are grown. Through these steps, a word line WL is formed. Further, using well-known fabrication steps, the magnetic memory device as shown inFIG. 1is manufactured.

As has been described above, after the magnetic film and Cu film are buried in the trench39, the entire surface of the resultant structure is subjected to wet etching. Subsequently, the Ta film that is deposited on the entire surface is polished until the surface of the insulation layer34is flattened. The Ta film is thus buried in the trench39. Thereby, the barrier metal layer38is formed on the Cu wiring layer37.

By the wet etching step, those portions of the Cu film and magnetic film, which are left on the drain contact DC-3and insulation layer34, can be removed. Therefore, a short-circuit due to the Cu film, etc., which are left on the drain contact DC-3and insulation layer34, can be prevented, and the reliability of the device can be enhanced.

On the other hand, by the wet etching step, the upper surface of the Cu film is recessed below the upper surface of the trench39and is distorted in an uneven shape. Then, the Ta film is polished down to the surface of the insulation layer34and is flattened. Thereby, the Ta film is buried in the trench39and the barrier metal layer38is formed on the Cu wiring layer37. Hence, the word line WL with the flattened upper surface can be formed.

Furthermore, the Cu wiring layer37is subjected to heat treatment, and grain boundaries of Cu metal in the Cu wiring layer37are grown. In the above-mentioned step, the barrier metal layer38is formed on the Cu wiring layer37, and it is thus possible to prevent the surface of the word line WL from becoming uneven due to the grown grain boundaries in the Cu wiring layer37. In addition, the grain boundaries of Cu metal in the Cu wiring layer37are grown, and the reliability of the Cu wiring layer37can be enhanced. As described above, the barrier metal layer38also functions as a barrier to the lower surface side of the barrier metal layer38, which prevents the surface of the word line WL from becoming uneven due to the grain boundaries that are grown in the Cu wiring layer37in the heat treatment step.

As has been described above, according to the method of manufacturing the magnetic memory device according to the present embodiment, those portions of the Cu film and magnetic film, which are left on the insulation layer34, can be removed by the wet etching step. Therefore, a short-circuit can be prevented and the insulation properties can be enhanced. Moreover, the barrier metal layer38is buried in the groove39over the Cu film that is recessed below the upper surface of the trench39and distorted in an uneven shape. Thereby, the word line WL with the flattened upper surface can be formed. Hence, in subsequent fabrication steps, the cross-sectional shape of the MTJ element that is formed on the word line WL can be made flat, and the distance between the word line WL and the MTJ element can be reduced.

Modification 1 of the magnetic memory device and the manufacturing method thereof according to the invention will now be described with reference toFIG. 4toFIG. 7. A description of the parts common to those in the first embodiment is omitted.

FIG. 4is a cross-sectional view that schematically shows the structure of a magnetic memory device according to Modification 1. A free layer41and a tunneling barrier layer42are provided on an underlying conductive layer40. Side walls of the free layer41and tunneling barrier layer42in the direction of the bit line BL are formed to be continuous. A pinned layer43is provided on the tunneling barrier layer42such that the length of the pinned layer43in the direction of bit line BL is less than the length of each of the free layer41and tunneling barrier layer42in the direction of bit line BL.

According to this magnetic memory device, the same advantages as with the first embodiment can be obtained. In addition, the magnetic memory device of Modification 1 is configured such that the side walls of the free layer41and tunneling barrier layer42in the direction of the bit line BL are formed to be continuous, and the pinned layer43is provided on the tunneling barrier layer42such that the length of the pinned layer43in the direction of bit line BL is less than the length of each of the free layer41and tunneling barrier layer42in the direction of bit line BL.

By virtue of this configuration, a distance44between the side wall of the free layer41and the side wall of the pinned layer43becomes greater than in the case where the side walls of the free layer41, tunneling barrier layer42and pinned layer43in the direction of the bit line BL are formed to be continuous. Therefore, the insulation between the free layer41and pinned layer43can be enhanced, and the reliability of the device increased. The thickness of the MTJ element (the total thickness of free layer41, tunneling insulation film42and pinned layer43) is, e.g. about several Å to several-ten Å. Therefore, Modification 1, in which the distance44is increased, is effective for miniaturization.

Referring now toFIG. 5toFIG. 7, a description is given of a method of manufacturing the magnetic memory device according to Modification 1, taking the magnetic memory device shown inFIG. 4by way of example.

To start with, using well-known fabrication steps, as illustrated inFIG. 5, a transistor TR and a word line WL are formed on a major surface of a semiconductor substrate31. Further, insulation layers35and50and an underlying conductive layer40are formed.

Subsequently, as illustrated inFIG. 6, a magnetic film55, an insulation layer56, a magnetic film57and a hard mask58-1are successively formed on the insulation layer50and underlying conductive layer40, using, e.g. CVD. A photoresist58-2is coated on the hard mask58-1.

Then, the photoresist58-2is exposed and developed to form a pattern for forming a free layer41and a tunneling barrier layer42. This pattern is transferred to the hard mask58-1, following which the photoresist58-2is removed by an asher. Using the pattern-transferred hard mask58-1as a mask, the entire surface of the structure is subjected to anisotropic etching, such as RIE (Reactive Ion Etching), down to the surface of the underlying conductive layer40. Thus, the free layer41and tunnel barrier layer42are formed.

Using similar fabrication steps, as illustrated inFIG. 7, a hard mask60-1, on which a pattern for forming a pinned layer is transferred, and a photo-resist60-2are successively formed on the magnetic film57. The hard mask60-1has openings for exposing end portions of the magnetic film57in the word line WL direction.

The photoresist60-2is then removed by the asher. Using the pattern-transferred hard mask60-1as a mask, the entire surface of the structure is subjected to anisotropic etching, such as RIE, down to the surface of the tunneling barrier layer52. Thus, the pinned layer43is formed. Subsequently, the hard mask60-1is removed. Similar fabrication steps are performed, and the magnetic memory device as shown inFIG. 4is manufactured.

According to the above-described manufacturing method, the same advantages as with the first embodiment can be obtained. Further in the manufacturing method of Modification 1, the free layer41and tunneling barrier layer42are first formed (FIG. 6) and then the pinned layer43is formed to have a less length than the free layer41and tunneling barrier layer42in the bit line BL direction (FIG. 7).

Thus, the pinned layer43and free layer41can be formed independently (FIG. 6,FIG. 7). In the step of forming the pinned layer43(FIG. 7), the surface of the free layer41is covered with the hard mask60-1. Thus, in the step of forming the pinned layer43, it is possible to prevent a part of the magnetic film57from extending beyond the tunneling barrier layer42and contacting the free layer41. Therefore, the insulation properties are improved, and the reliability is enhanced.

In each of the steps of forming the free layer41and pinned layer43, the photoresist58-2,60-2is not directly coated on the magnetic film55,57, but is formed on the hard mask58-1,58-2. Therefore, when the photoresist58-2,60-2is removed by the asher, it is possible to prevent the magnetism of the magnetic film55,57from deteriorating.

A magnetic memory device and a method of manufacturing the same according to a second embodiment of the present invention will now be described with reference toFIG. 8toFIG. 11. A description of the parts common to those in the first embodiment is omitted.FIG. 8is a cross-sectional view that schematically shows the structure of the magnetic memory device according to the second embodiment of the invention. The magnetic memory device according to the second embodiment is applied to a so-called cross-point type MRAM.

An MTJ element is provided at an intersection between a word line WL and a bit line BL over a major surface of a semiconductor substrate31. The MTJ element is so provided as to contact a barrier metal layer38of a word line WL.

This structure can bring about the same advantages as with the first embodiment. In addition, the magnetic memory device according to the second embodiment is a so-called cross-point type MRAM wherein the MTJ element is so provided as to contact the barrier metal layer38. Thus, compared to the 1T1MTJ type MRAMs according to the first embodiment and Modification 1, the transistor TR, insulation layer35and underlying conductive layer40can be dispensed with, and miniaturization can more effectively be achieved.

Next, referring toFIG. 9toFIG. 11, a description is given of a method of manufacturing the magnetic memory device according to the second embodiment, taking the magnetic memory device shown inFIG. 8by way of example.

To start with, using the same fabrication steps as described above, a yoke layer36, a Cu wiring layer37and a barrier metal layer38are formed in an insulation layer61on the major surface of a semiconductor substrate31, thereby forming a word line WL, as illustrated inFIG. 9.

Then, as illustrated inFIG. 10, a magnetic film55, an insulation layer56, a magnetic film57and a hard mask70-1are successively formed on the insulation layer61, yoke layer36and barrier metal layer38, using, e.g. CVD. A photoresist70-2is coated on the hard mask70-1. The photoresist70-2is exposed and developed so that a pattern for forming the MTJ element is formed on the photoresist70-2. This pattern is transferred to the hard mask70-1. Then, the photoresist70-2is removed by the asher.

As is shown inFIG. 11, using the pattern-transferred hard mask70-1as a mask, the surface of the structure is subjected to anisotropic etching, such as RIE, down to a surface71of the barrier metal layer38. Thus, the MTJ element is formed. The hard mask70-1is then removed. Through similar fabrication steps, the magnetic memory device as shown inFIG. 8is manufactured.

According to the above-described manufacturing method, the same advantages as with the first embodiment can be obtained. In addition, in the step of forming the MTJ element (FIG. 11), the anisotropic etching is carried out down to the surface71of the barrier metal layer38. Thus, the anisotropic etching is performed in the state in which the Cu wiring layer37with low hardness is not exposed and is covered with the barrier metal layer38. Therefore, recessing or chipping of the Cu wiring layer37can be prevented. Further, as regards a so-called milling step that mainly involves a physical processing step and is performed prior to the anisotropic etching step, the Cu wiring layer37is not directly exposed. Thus, recessing or chipping of the Cu wiring layer37can be prevented, and the reliability of the word line WL can be improved. As described above, the barrier metal layer38also serves as a barrier to the surface side of the barrier metal layer38in order to prevent recessing or chipping of the Cu wiring layer37in the anisotropic etching step and milling step.

A magnetic memory device according to Modification 2 of the invention and a method of manufacturing the same will now be described with reference toFIG. 12. A description of the parts common to the first and second embodiments and Modification 1 is omitted.FIG. 12is a cross-sectional view that schematically shows the structure of the magnetic memory device according to Modification 2.

In Modification 2, the yoke layer comprises a plurality of layers. A first yoke layer75is provided in the trench in the insulation layer61. A second yoke layer76is laid over the first yoke layer75. The first yoke layer75is formed of a ferromagnetic material including a high-permeability magnetic material such as NiFe or CoFeNi. Similarly, the second yoke layer76is formed of a ferromagnetic material including a high-permeability magnetic material such as NiFe or CoFeNi.

The first yoke layer75and second yoke layer76are formed in the trench by means of, e.g. sputtering. Alternatively, MOCVD (Metal Organic Chemical Vapor Deposition) or CVD may be adopted. In the other respects, the same steps as described above are performed to manufacture the magnetic memory device shown inFIG. 12.

According to the above-described magnetic memory device and the manufacturing method thereof, the same advantages as with the second embodiment can be obtained. In addition, in the magnetic memory device according to Modification 2, the yoke layer has a multi-layer structure, and the first yoke layer75is provided in the trench in the insulation layer61and the second yoke layer76is laid over the first yoke layer75. Moreover, each of the first yoke layer75and second yoke layer76is formed of a ferromagnetic material including a high-permeability magnetic material. Therefore, in the data write operation, of the magnetic fluxes generated from the word line WL, magnetic fluxes that come from the bottom and side surfaces of the word line WL are led to the yoke layers75and76, and the write current can more effectively be reduced.

Magnetic memory devices according to Modification 3 of the invention and methods of manufacturing the same will now be described with reference toFIG. 13andFIG. 14. A description of the parts common to the first and second embodiments and Modifications 1 and 2 is omitted.FIG. 13andFIG. 14are cross-sectional views that schematically show the structures of the magnetic memory devices according to Modification 3.

In Modification 3, a diode layer72is additionally provided between the cross-point type MTJ element and the word line WL. InFIG. 13, a diode layer72is provided in an insulation layer62that is formed on the barrier metal layer38. The MTJ element is provided on the diode layer72. InFIG. 14, the yoke layer comprises two yoke layers75and76, and a diode layer72is additionally provided. These magnetic memory devices are manufactured through well-known fabrication steps, and a detailed description is omitted. The diode layer72is, for example, a PN junction diode layer that is formed of silicon.

The diode layer72may be provided between the MTJ element and the bit line BL.

According to the above-described magnetic memory devices, the same advantages as with the second embodiment and Modification 2 can be obtained. In the magnetic memory devices according to Modification 3, the diode layer72is additionally provided between the MTJ element and the word line WL.

This structure can prevent a current which flows to an adjacent MTJ element at a time of a write/read operation of an MTJ element. Therefore, the reliability of the magnetic memory device is further improved.

It should suffice if only one diode layer72is provided between the MTJ element and the word line WL or between the MTJ element and the bit line BL. Since the cell area in the bit line BL direction does not increase, this structure is effective for miniaturization.

Fourth modification4of the magnetic recording apparatus and method of manufacturing the apparatus will be described, with reference toFIG. 15.FIG. 15is a sectional view of the magnetic recording apparatus according to the fourth modification. The components identical to those of the first, second and third modifications will not be described.

AsFIG. 15shows, a barrier metal layer77-1is provided at the interface between the yoke layer36and the wiring layer37and a barrier metal layer77-2is provided at the interface between the yoke layer36and the insulating layer61. These layers77-1and77-2are formed by a method known in the art.

Having the structure ofFIG. 15, the apparatus achieves the same advantages as the first, second and third modifications. Further, the barrier metal layer77-1prevents the material of the yoke layer36from diffusing into the wiring layer37, and the material of the wiring layer37from diffusing into the yoke layer36. Similarly, the barrier layer77-2prevents the material of the yoke layer36from diffusing into the insulating layer61, and the material of the insulating layer61from diffusing into the yoke layer36. Thus, the yoke layer36can maintain its magnetic characteristics. In short, the barrier metal layers77-1and77-2help to maintain the magnetic characteristics of the yoke layer36.

Needless to say, the barrier metal layers77-1and77-2can be provided in the embodiments described above, and also in the first, second and third modifications.

In the first and second embodiments and Modifications 1 to 4, MTJ elements are employed by way of example. The present invention, however, is not limited to MTJ elements and is applicable to magnetic memory devices including other magneto-resistance effect elements such as GMR (Giant Magneto-Resistance) elements and CMR (Colossal Magneto-Resistance) elements.

In the first and second embodiments and Modifications 1 to 4, the Cu wiring layer37is used as the wiring layer of the word line WL by way of example. Other metal layers, such as an Al wiring layer, may be used.