Abstract:
According as the gap layer formed between the magnetoresistive effect element and the shielding layer becomes smaller along with the recent tendency toward a higher recording density, the electrode layer of the magnetoresistive effect element and the shielding layer have been electrically connected, and this has caused a deterioration of the reproduction property. An insulating layer is formed under an electrode layer of a magnetoresistive effect element interposed a lower gap layer therebetween. As a result, the distance between the electrode layer and the lower shielding layer becomes longer, thus permitting maintenance of a satisfactory electrical insulation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a thin-film magnetic head having a magnetoresistive effect element using magnetoresistive effect of a spin valve film or the like. More particularly, the present invention relates to a thin-film magnetic head giving an improved electrical insulation between the electrode layer of the magnetoresistive effect element and the lower shielding layer, and a manufacturing method thereof.  
           [0003]    2. Description of the Related Art  
           [0004]    [0004]FIG. 21 is an enlarged sectional view illustrating a conventional thin-film magnetic head as viewed from the opposite side of a recording medium (ABS (air bearing surface) plane).  
           [0005]    This thin-film magnetic head is a read head using the magnetoresistive effect, formed on a trailing side end surface of a slider constituting, for example, a floating-type head. The thin-film magnetic head may be a head formed by laminating a write inductive magnetic head on the aforementioned read head, known generally as an MR(magnetoresistive)/inductive composite thin-film magnetic head.  
           [0006]    In FIG. 21, the reference numeral  1  represents a lower shielding layer formed from Sendust or an NiFe alloy (permalloy), and a lower gap layer  4  made of a non-magnetic material such as Al 2 O 3  (alumina) is formed on the lower shielding layer  1 . A magnetoresistive effect element  5  is formed in the form of a film on the above-mentioned lower gap layer  4 . A multilayer film  6  using the magnetoresistive effect is formed at the center of the magnetoresistive effect element  5 .  
           [0007]    The aforementioned multilayer film  6  comprises a spin-valve film (a kind of GMR (gaiant magnetoreistive) element having, for example, an anti-ferromagnetic layer, a fixed magnetic layer, a non-magnetic conductive layer, and a free magnetic layer. In this spin-valve film, magnetization of the fixed magnetic layer is fixed in a direction perpendicular to the plane of the drawing (Y-direction: height direction), and magnetization of the free magnetic layer is aligned with the track transverse direction (X-direction). When the magnetic field from the recording medium penetrates in the direction perpendicular to the plane of drawing, magnetization of the free magnetic layer varies, and electric resistance varies under the effect of the relationship between fixed magnetization of the fixed magnetic layer and varying magnetization of the free magnetic layer, thus reproducing the recording magnetic field.  
           [0008]    As shown in FIG. 21, a hard bias layer  7  and an electrode layer  8  made of a non-magnetic conductive material having a low electric resistance such as Cr (chromium) or Ta (tantalum) are formed as a longitudinal bias layer on each of the both sides of the multilayer film  6 .  
           [0009]    An upper gap layer  9  is formed on the magnetoresistive effect element  5 , and further, an upper shielding layer  10  is formed on the upper gap layer  9 .  
           [0010]    Also as shown in FIG. 21, the lower gap length GL 1  is determined from the thickness of the lower gap layer  4  formed under the magnetoresistive effect element  5 , and the upper gap length GL 2  is determined from the thickness of the upper gap layer  9  formed on the magnetoresistive effect element  5 . The read gap length GL is set from the thickness of the magnetoresistive effect element  5 , the lower gap length GL 1  and the upper gap length GL 2 .  
           [0011]    [0011]FIG. 22 is a plan view of the magnetoresistive effect element  5  formed on the lower gap layer  4 . As shown in FIG. 22, the multilayer film  6  and the electrode layer  8  forming the magnetoresistive effect element  5  are exposed to the ABS plane serving as an opposite surface to the recording medium, and the electrode layer  8  extends to the rear side (Y-direction: height direction) from the multilayer film  6 . The electrode layer  8  is formed so as to become larger in width toward the rear side.  
           [0012]    Along with the recent tendency toward a higher recording density, it is necessary to form the lower gap length GL 1  and the upper gap length GL 2  shown in FIG. 21 into smaller sizes.  
           [0013]    However, when the gap layers  4  and  9  are formed into smaller thickness with a view to reducing the sizes of the lower gap length GL 1  and the upper gap length GL 2 , defects such as pinholes are produced in the gap layers  4  and  9  serving to maintain insulation between the shielding layers  1  and  10  and the magnetoresistive effect element  5 , resulting in electric connection between the shielding layers  1  and  10  and the magnetoresistive effect element  5 .  
           [0014]    Particularly, the above-mentioned problem tends to be caused between the electrode layer  8  having a large width formed on the rear side from the ABS plane and the shielding layers  1  and  10  as shown in FIG. 22, resulting in a lower reproducing property due to electric connection between the shielding layers  1  and  10  and the electrode layer  8 .  
           [0015]    Upon manufacturing a thin-film magnetic head, the ABS plane of the multilayer film  6  is ground (height-making fabrication in the height direction (Y-direction in FIG. 22) until DC resistance of the multilayer film  6  shown in FIG. 22. This height-making fabrication causes smearing between the shielding layers  1  and  10  and the electrode layers  8  and  8 , tending to make electric connection between the shielding layers  1  and  10  and the electrode layers  8  and  8 .  
           [0016]    When the shielding layers  1  and  10  and the electrode layers  8  and  8  are electrically connected, a problem is that the height-making fabrication cannot be applied while appropriate measuring DC resistance of the multilayer film  6 .  
         SUMMARY OF THE INVENTION  
         [0017]    The present invention was developed for the purpose of solving the conventional problems as described above, and relates to a thin-film magnetic head which can maintain an appropriate electric insulation between the shielding layer and electrode layer of the magnetoresistive effect element even for a small gap length and permits obtaining a stable reproducing property, thereby coping with the tendency toward a higher recording density, and a manufacturing method thereof.  
           [0018]    The present invention provides a thin-film magnetic head comprising a lower shielding layer and a lower gap layer formed thereon, a magnetresistive element comprising a multilayer fril displaying magnetoresistive effect and formed on said lower gap layer and an electrode layer connected to said multilayer film, and an upper shielding layer formed on the magnetoresistive effect element via the upper gap layer; wherein an insulating layer is formed in addition to the lower gap layer between the electrode layer and the lower shielding layer.  
           [0019]    In the invention, the insulating layer should preferably be arranged at least on each of the both sides of the multilayer film or a reproducing track width.  
           [0020]    In the invention, furthermore, the lower gap layer and the insulating layer should preferably have a total thickness of at least 700 Å.  
           [0021]    In a detailed structure in the invention, an insulating layer should preferably be formed on the lower shielding layer, and the electrode layer should preferably be formed on the insulating layer interposed the lower gap layer therebetween.  
           [0022]    A slant should preferably be formed on each of the sides of the insulating layer.  
           [0023]    In the invention, the insulating layer should preferably be formed with one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4  and AlN.  
           [0024]    In a detailed structure in the invention, a recess should preferably be formed on the surface of the lower shielding layer, with an insulating layer formed in the recess, and the electrode should preferably be formed on the insulating layer interposed the lower gap layer therebetween.  
           [0025]    In this case, the surface of the lower shielding layer should preferably be flush with the surface of the insulating layer formed in the recess of the lower shielding layer.  
           [0026]    In the invention, the insulating layer formed under the electrode layer should preferably be formed by exposing up to an ABS plane.  
           [0027]    As in the configuration described above, in the invention, it is possible to maintain a satisfactory level of electric insulation between the electrode layer and the shielding layer by forming an insulating layer, in addition to the lower gap layer, between the electrode layer and the lower shielding layer.  
           [0028]    The invention further provides a thin-film magnetic head comprising a lower shielding layer and a lower gap layer formed thereon, a magnetoresistive effect element comprising a multilayer film displaying a magnetoresistive effect and formed on said lower gap layer and an electrode layer connected to the multilayer film, and an upper shielding layer formed on the magnetoresistive effect element interposed the upper gap layer therebetween; wherein an insulating layer is formed in addition to the upper gap layer between the electrode layer and the upper shielding layer.  
           [0029]    In the invention, the insulating layer should preferably be arranged at least on each of the both sides of the multilayer film or a reproducing track width.  
           [0030]    In the invention, furthermore, the lower gap layer and the insulating layer should preferably have a total thickness of at least 700 Å.  
           [0031]    In the invention, an insulating layer should preferably be formed on the electrode layer interposed the upper gap layer therebetween. A slant should preferably be formed on each of the sides of the insulating layer.  
           [0032]    In the invention, furthermore, the insulating layer should preferably be formed with one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4  and AlN.  
           [0033]    In another detailed structure in the invention, an insulating layer should preferably be formed on the electrode layer, and further, an upper gap layer should preferably be formed on the insulating layer.  
           [0034]    In the invention, the insulating layer formed on the electrode layer should preferably be formed by exposing up to an ABS plane.  
           [0035]    As in the above-mentioned configuration of the invention, it is possible to maintain a satisfactory level of electric insulation between the electrode layer and the shielding layer by forming the insulating layer, in addition to the upper gap layer, between the electrode layer and the upper shielding layer.  
           [0036]    The present invention further provides a thin-film magnetic head comprising a lower shielding layer and a lower gap layer formed thereon, a magnetoresistive effect element having a multilayer film formed on the lower gap layer and connected to the multilayer film, and an upper shielding layer formed on the magnetoresistive effect element via the upper gap layer; wherein the insulating layer is formed between the electrode layer and the lower shielding layer, and the insulating layer is formed between the electrode layer and the upper shielding layer.  
           [0037]    Further, the invention provides a manufacturing method of a thin-film magnetic head, comprising:  
           [0038]    a step of forming an insulating material layer on a lower shielding layer;  
           [0039]    a step of forming a resist layer on the insulating material layer;  
           [0040]    a step of removing the insulating material layer not covered with the resist layer to retain the insulating material layer formed under the resist layer as an insulating layer;  
           [0041]    a step of forming a lower gap layer on an area covering the insulating layer and the lower shielding layer, after removing the resist layer;  
           [0042]    a step of forming an electrode layer of a magnetoresistive effect element on the lower gap layer overlapping the insulating layer, and forming a multilayer film displaying magnetoresistive effect on the lower gap layer; and  
           [0043]    a step of forming an upper gap layer on the magnetoresistive effect element formed on the lower gap layer, and forming an upper shielding layer on the upper gap layer.  
           [0044]    When using the above-mentioned manufacturing method, it is recommendable to form a slant on a side of the insulating layer retained under the resist layer by the use of isotropic etching after forming the resist layer on the insulating material layer.  
           [0045]    Or, it is desirable to form a resist layer on the insulating material layer, then, form a slant on a side of the resist layer surface by applying a heat treatment to the resist layer, and form a slant on the other side of the insulating layer under the resist layer by the use of anisotropic etching.  
           [0046]    In order to use isotropic etching or anisotropic etching, it is desirable to form the insulating material layer with one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 3 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4  and AlN.  
           [0047]    In the present invention, the aforementioned method for forming the insulating layer upon forming the insulating layer on the electrode layer interposed the upper gap layer therebetween.  
           [0048]    The invention further provides a manufacturing method of a thin-film magnetic head, comprising:  
           [0049]    a step of forming a resist layer for lifting off on a lower shielding layer;  
           [0050]    a step of forming a recess on the surface of the lower shielding layer by applying etching to the surface of the lower shielding layer not covered with the resist layer;  
           [0051]    a step of forming an insulating layer in the recess formed on the surface of the lower shielding layer;  
           [0052]    a step of removing the resist layer and forming a lower gap layer on an area covering the insulating layer and the lower shielding layer;  
           [0053]    a step of forming an electrode layer of a magnetoresistive effect element on the lower gap layer overlapping the insulating layer, and forming a multilayer film displaying a magnetoresistive effect on the lower gap layer not having an insulating layer formed thereon; and  
           [0054]    a step of forming an upper gap layer on the magnetoresistive effect element formed on the lower gap layer, and further, forming an upper shielding layer on the upper gap layer.  
           [0055]    When using the aforementioned manufacturing method, it is desirable to form the insulating layer in a recess formed on the lower shielding layer so that the surface of the insulating layer is flush with the surface of the lower shielding layer.  
           [0056]    By using the aforementioned manufacturing method, it is possible to easily form the insulating layer between the shielding layer and the electrode layer, and hence, to achieve satisfactory electric insulation between the shielding layer and the electrode layer.  
           [0057]    The present invention further provides a manufacturing method of a thin-film magnetic head, comprising:  
           [0058]    a step of forming a multilayer film displaying a magnetoresistive effect on the entire surface of the lower gap layer;  
           [0059]    a step of forming a lift-off resist layer on the multilayer film, and removing the multilayer film not covered with the lift-off resist layer by etching;  
           [0060]    a step of forming an electrode layer on the lower gap layer, from which the multilayer film has been removed in the preceding step, and forming an insulating layer on the electrode layer; and  
           [0061]    a step of removing the lift-off resist layer, and forming the upper gap layer on an area covering the multilayer film and the insulating layer.  
           [0062]    By using this method, it is possible to easily form the insulating layer in addition to the upper gap layer between the electrode layer and the upper shielding layer. According to the aforementioned method, furthermore, it is possible to completely cover the entire upper surface of the electrode layer with the insulating layer, thus permitting maintenance of a further better electric insulation between the upper shielding layer and the electrode layer. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0063]    [0063]FIG. 1 is a partial plan view illustrating the structure of a magnetoresistive effect element forms on a lower gap layer in the present invention;  
         [0064]    [0064]FIG. 2 is a partial sectional view of FIG. 1 cut along the line  2 - 2 ;  
         [0065]    [0065]FIG. 3 is a partial sectional view illustrating the structure of a thin-film magnetic head of a second embodiment of the invention;  
         [0066]    [0066]FIG. 4 is a partial sectional view illustrating the structure of a thin-film magnetic head of a third embodiment of the invention;  
         [0067]    [0067]FIG. 5 is a partial sectional view illustrating the structure of a thin-film magnetic head of a fourth embodiment of the invention;  
         [0068]    [0068]FIG. 6 is a process diagram illustrating a manufacturing method of a thin-film magnetic head of the invention;  
         [0069]    [0069]FIG. 7 is a process diagram of a process next to that shown in FIG. 6;  
         [0070]    [0070]FIG. 8 is a process diagram of a process next to that shown in FIG. 7;  
         [0071]    [0071]FIG. 9 is a process diagram of a process next to that shown in FIG. 8;  
         [0072]    [0072]FIG. 10 is a process diagram illustrating a second manufacturing method of a thin-film magnetic head of the invention;  
         [0073]    [0073]FIG. 11 is a process diagram of a process next to that shown in FIG. 10;  
         [0074]    [0074]FIG. 12 is a process diagram of a process next to that shown in FIG. 11;  
         [0075]    [0075]FIG. 13 is a process diagram of a process next to that shown in FIG. 12;  
         [0076]    [0076]FIG. 14 is a process diagram illustrating a third manufacturing method of a thin-film magnetic head of the invention;  
         [0077]    [0077]FIG. 15 is a process diagram of a process next to that shown in FIG. 14;  
         [0078]    [0078]FIG. 16 is a process diagram of a process next to that shown in FIG. 15;  
         [0079]    [0079]FIG. 17 is a process diagram of a process next to that shown in FIG. 16;  
         [0080]    [0080]FIG. 18 is a process diagram illustrating a fourth manufacturing method of a thin-film magnetic head of the invention;  
         [0081]    [0081]FIG. 19 is a process diagram of a process next to that shown in FIG. 18;  
         [0082]    [0082]FIG. 20 is a process diagram of a process next to that shown in FIG. 19;  
         [0083]    [0083]FIG. 21 is a partial sectional view illustrating the structure of a thin-film magnetic head in the conventional art; and  
         [0084]    [0084]FIG. 22 is a partial plan view illustrating the structure of a magnetoresistive effect element formed on a lower gap layer in the conventional art. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0085]    [0085]FIG. 1 is a partial plan view of a magnetoresistive effect element formed in a thin-film magnetic head (read head) of the present invention; and FIG. 2 is a partial sectional view of the thin-film magnetic head shown in FIG. 1 cut along the line  2 - 2 .  
         [0086]    The read head detects a leaking magnetic field from a recording medium such as a hard disk by the utilization of magnetoresistive effect to read out a recorded signal. The thin-film magnetic of the invention may be a head known as a composite thin-film magnetic head in which a write inductive magnetic head is laminated on the read head. The lower shielding layer  20  shown in FIG. 2 made of a soft magnetic material is formed on the trailing end surface of the slider.  
         [0087]    As shown in FIG. 2, a lower gap layer  21  made of a non-magnetic material such as Al 2 O 3  (alumina) is provided on the lower shielding layer  20 . A magnetoresistive effect element  22  is formed on the lower gap layer  21 . A multilayer film  23  displaying magnetoresistive effect is formed at the center of the magnetoresistive effect element  22 . The multilayer film  23  is, for example a GMR element using giant magnetoresistive effect typically represented by a spin-valve film or an AMR element using anisotropic magnetoresistive effect.  
         [0088]    The above-mentioned spin-valve film is composed of a four-layer structure comprising an antiferromagnetic layer, a fixed magnetic layer, a non-magnetic conductive layer, and a free magnetic layer, the simplest structure. Of these four layers, the anti-ferromagnetic layer has the largest thickness.  
         [0089]    As shown in FIG. 2, a hard bias layer  24  and an electrode layer  25  (Cr (chromium) or Ta (tantalum)) are formed on each of he both sides of the multilayer film  23 . For example, a bias magnetic filed is given by the hard magnetic bias layer to the free magnetic layer of the spin-valve film, whereby magnetization of the free magnetic layer is aligned in the track width direction. Magnetization of the fixed magnetic layer of the spin-valve film is, on the other hand, fixed by an exchange bonding magnetic field with the anti-ferromagnetic layer in a direction perpendicular to the plane of paper of the drawing (height direction: Y-direction). When the magnetic field from the recording medium enters in a direction perpendicular to the drawing plate, magnetization of the free magnetic layer aligned in the track width direction varies, electric resistance varies under the effect of the relationship between the varying magnetization of the free magnetic layer and the fixed magnetization of he fixed magnetic layer, whereby a recording signal is detected. A reproducing track width RTw is formed by the distance between the electrode layers  25  and  25 .  
         [0090]    As shown in FIG. 2, the upper gap layer  26  made of Al 2 O 3  (alumina) is formed on the multilayer film  23  and the electrode layer  25 , and further, an upper shielding layer  27  is formed on the upper gap layer  26 . When the thin-film magnetic head of the invention is a composite thin-film magnetic head made by laminating the read head and an inductive head, the upper shielding layer  27  simultaneously has a shielding function of the read head and a function as a trailing-side core of the inductive magnetic head.  
         [0091]    As shown in FIG. 2, a lower gap length GL 1  is determined by the thickness of the lower gap layer  21 , and an upper gap length GL 2  is determined by the thickness of the upper gap layer  26 . A read gap length GL is set by the total thickness of the lower gap length GL 1  and the upper gap length GL 2 .  
         [0092]    In the invention, an insulating layer  28  having a prescribed expanse is formed on the lower shielding layer  20 , and an electrode layer  25  of the magnetoresistive effect element  22  is formed on the insulating layer  28  interposed the lower gap layer  21  therebetween.  
         [0093]    No insulating layer  28  is formed, as shown in FIG. 2, under the multilayer film  23  composed of a spin-valve film or the like. If an insulating layer  28  is formed under the multilayer film  23 , the substantial lower gap length GL 1  between the multilayer film  23  and the lower shielding layer  20  would become excessively large and cannot cope with the tendency toward a higher recording density.  
         [0094]    Therefore, the insulating layers  28  and  28  should preferably be arranged on the both sides of the multilayer film  23 , or on the both sides of the reproducing track width RTw. This arrangement permits reduction of the lower gap length GL 1  within the reproducing track width TRw, coping with the tendency toward a higher recording density, improvement of insulation within the reproducing track width, and inhibition of occurrence of smearing.  
         [0095]    Also as shown in FIG. 2, the insulating layer  28  has a thickness h 1 . In the invention, the insulating layer  28  thickness h 1  and the lower gap length GL 1  should preferably have a total thickness of at least 700 Å. With a thickness of at least 700 Å, it is possible to maintain a satisfactory electric insulation between the electrode layer  25  and the lower shielding layer  20 .  
         [0096]    Further as shown in FIG. 2, a slant  28   a  should preferably be formed on each of the sides of the insulating layer  28 . By providing the insulating layer  28  on the lower shielding layer  20 , a step is produced on the surface of the lower gap layer  21  at a position where the magnetoresistive effect element  22  is to be formed. By providing the slant  28   a  on the insulating layer  28 , it is possible to form the surface of the lower gap layer  21  into a slow step, and inhibit a decrease in the pattern accuracy upon forming the magnetoresistive effect element  22 .  
         [0097]    In order to form the slant  28   a  on the side of the insulating layer  28 , anisotropic etching or isotropic etching is used as described later. With a view not to causing a damage to the surface of the lower shielding layer, a material for the insulating layer  28  is appropriately selected.  
         [0098]    In the invention, the insulating layer should preferably be made of one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4 , and AlN.  
         [0099]    The range of formation of the insulating layer  28  will now be described.  
         [0100]    As shown in FIG. 1, the multilayer film  23  composing the magnetoresistive effect element  22 , the hard magnetic bias layers (not shown) formed on the both sides of the multilayer film  23  and the electrode layer  25  are exposed on the ABS (air bearing surface) plane as well, and the electrode layer  25  extends beyond the multilayer film  23  and the hard magnetic bias layer further rearward (in the height direction: Y-direction).  
         [0101]    As shown in FIG. 1, the electrode layer  25  is formed so that the width thereof becomes larger from the ABS plane toward the rear side.  
         [0102]    Also as shown in FIG. 1, the insulating layer (within the range marked with dots)  28  formed between the lower gap layer  21  and the lower shielding layer  20  (see FIG. 2) is formed on substantially the entire region under the electrode layer  25  forming the magnetoresistive effect element  22 . As shown in FIG. 1, the insulating layer  28  is not formed under the multilayer film  23  composing the magnetoresistive effect element  22 .  
         [0103]    In the invention, as shown in FIG. 1, the insulating layer  28  is formed to reach the ABS plane and is exposed from the ABS plane. In this exposed state of the insulating layer  28  from the ABS plane, the distance between the electrode layer  25  and the lower shielding film  20  becomes longer as compared with the conventional art in the presence of the insulating layer  28 . Therefore, even when smearing is caused between the electrode layer  25  and the lower shielding layer  20  by grinding upon application of a grinding fabrication for achieving a prescribed length of the multilayer film in the height direction through grinding (height-making fabrication) of the ABS plane of the multilayer film  23 , electric connection between the electrode layer  25  and the lower shielding layer  20  becomes more difficult, thus permitting height-making fabrication appropriately while measuring DC resistance value of the multilayer film  23 .  
         [0104]    While the forming range of the insulating layer  28  may be outside the range shown by a dotted line in FIG. 2, the insulating layer  28  should preferably be formed under the electrode layer  25  formed with a larger width at least on the rear side of the multilayer film  23 . In the rear region, the electrode layer  25  occupies a large area on the lower gap layer  21 . Therefore, upon occurrence of pinholes or the like in the lower gap layer  21 , the lower shielding layer  20  and the electrode layer  25  become more easily connectable electrically.  
         [0105]    [0105]FIG. 3 is a partial sectional view illustrating the structure of another embodiment of the thin-film magnetic head of the invention. In FIG. 3, the upper gap layer  26  and the upper shielding layer  27  (see FIG. 2) formed on the magnetoresistive effect element  22  are omitted.  
         [0106]    A recess  20   a  having a certain depth h 2  is formed on the surface of the lower shielding layer  20  shown in FIG. 3, and an insulating layer  29  is formed in this recess  20   a.    
         [0107]    In the invention, the surface of the insulating layer  29  should preferably be flush with the surface of the lower shielding layer  20 . By forming the surface of the insulating layer  29  flush with the surface of the lower shielding layer  20 , it is possible to improve the pattern accuracy upon forming the magnetoresistive effect element  22 .  
         [0108]    As shown in FIG. 3, a lower gap layer  21  is formed on an area covering both the insulating layer  29  surface and the lower shielding layer  20  surface. In the invention, the total thickness of the thickness h 2  of the insulating layer  29  and the thickness (gap length) GL 1  of the lower gap layer  21  should preferably at least 700 Å. The magnetoresistive effect element  22  is formed on the lower gap layer  21 .  
         [0109]    Also as shown in FIG. 3, the multilayer film  23  forming the magnetoresistive effect element  22  is formed on the lower gap layer  21  on which an insulating layer  29  is not formed. The electrode layer  25  formed in expansion on the rear side (in the Y-direction in the drawing) of the multilayer film  23  (see FIG. 1) is formed on the lower gap layer  21  having the insulating layer  29  formed thereon.  
         [0110]    The insulating layer  29  in this embodiment may be made of any insulating material including, for example, Al 2 O 3  (alumina) used conventionally as an insulating material.  
         [0111]    In this embodiment as well, the insulating layer  29  should preferably be exposed up to the ABS plane, because, even upon occurrence of smearing, electric contact become more difficult between the lower shielding layer  20  and the electrode layer  25  forming the magnetoresistive effect element  22 . It is thus possible to apply height-making fabrication while appropriately measuring DC resistance value of the multilayer film  23 .  
         [0112]    In the embodiments shown in FIGS.  1  to  3 , the insulating layers  28  and  29  are formed between the lower shielding layer  20  and the lower gap layer  21 . In the invention, however, the insulating layer may be formed on the lower shielding layer  20  via the lower gap layer  21 .  
         [0113]    [0113]FIG. 4 is a partial sectional view illustrating the structure of another embodiment of the thin-film magnetic head of the invention.  
         [0114]    In FIG. 4, an insulating layer  30  is formed on the upper gap layer  26  formed on the magnetoresistive effect element  22 . The insulating layer  30  is formed on the electrode layer  25  forming the magnetoresistive effect element  22 . The insulating layer  30  is not formed on the multilayer film  23 .  
         [0115]    As shown in FIG. 4, the insulating layer  30  is formed with a thickness h 3 . In the invention, the total thickness of the thickness of the insulating layer  30  and the thickness of the upper gap layer  26  (upper gap length) should preferably be at least 700 Å. This is to improve electric insulation between the electrode layer  25  and the upper shielding layer  27 . A reproducing track width RTw is formed by the distance between the electrode layers  25  and  25 .  
         [0116]    A slant  30   a  should preferably be formed on the side of the insulating layer  30 .  
         [0117]    Further, in the invention, the insulating layer  30  should preferably be formed to reach the ABS plane, and exposed from the ABS plane.  
         [0118]    The insulating layer  30  should preferably be made of one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4  and AlN, as in the insulating layer  28  formed between the lower shielding layer  20  and the lower gap layer  21  shown in FIG. 2, by the use of anisotropic etching, isotropic etching or the lift-off method.  
         [0119]    As shown in FIG. 4, by forming the insulating layer  30 , in addition to the upper gap layer  26 , between the electrode layer  25  and the upper shielding layer  27 , the distance between the electrode layer  25  and the upper shielding layer  27  becomes longer as compared with the conventional art. Even upon occurrence of defects such as pinholes in the electrode layer  25 , it is possible to keep a satisfactory electrical insulation between the electrode layer  25  and the upper shielding layer  27 . Moreover, when the insulating layer is exposed to reach the ABS plane, it is possible to keep a satisfactory electrical insulation between the electrode layer  25  and the upper shielding layer  27  and carry out height-making fabrication appropriately while measuring DC resistance value of the multilayer film, when applying height-making fabrication.  
         [0120]    The insulating layers  30  and  30  should preferably be arranged on the both sides of the multilayer film  23  or on the both sides of the reproducing track width RTw. By adopting this position, it is possible to reduce the upper gap length GL 2  within the range of the reproducing track width RTw, cope with the tendency toward a higher recording density, improve insulation outside the range of the reproducing track width, and inhibit occurrence of smearing.  
         [0121]    In FIG. 4, the insulating layer  28  having the slant  28   a  is formed on the lower shielding layer  20 , and further, the lower gap layer  21  is formed over an area covering the insulating layer  28  and the lower shielding layer  20 . In the invention, as in the embodiment shown in FIG. 3, a recess  20   a  may be formed on the lower shielding layer  20 , and the insulating layer  29  may be formed in this recess  20   a . It is not always necessary to form the insulating layers  28  and  29  between the lower shielding layer  20  and the electrode layer  25 .  
         [0122]    [0122]FIG. 5 is a partial sectional view illustrating the structure of another embodiment of the thin-film magnetic head of the invention.  
         [0123]    In this embodiment also, as in FIG. 4, an insulating layer  40  is formed, in addition to the upper gap layer  26 , between the electrode layer  25  and the upper shielding layer  27 . In FIG. 5, the insulating layer  40  is formed directly on the upper surface of the electrode layer  25 .  
         [0124]    In FIG. 5, the entire upper surface of the electrode layer  25  is completely covered with the insulating layer  40 . As compared with the embodiment shown in FIG. 4, it is possible to achieve a better electrical insulation between the electrode layer  25  and the upper shielding layer  27 .  
         [0125]    The insulating layer  40  may be made of any insulating material including, for example, Al 2 O 3  (alumina) used conventionally as an insulating material.  
         [0126]    In FIG. 5, the insulating layer  40  should preferably be exposed to reach the ABS plane.  
         [0127]    As shown in FIG. 5, the insulating layer  40  is formed with a thickness h 7 , and the total thickness of the film thickness h 7  and the thickness of the upper gap layer  26  (upper gap length) GL 2  should preferably be at least 700 Å. This is to improve electrical insulation between the electrode layer  25  and the upper shielding layer  27 .  
         [0128]    In the embodiment shown in FIG. 5, as described above, the insulating layer  40  is formed between the electrode layer  25  and the upper shielding layer  27 , thus making it possible to keep a satisfactory electrical insulation between the electrode layer  25  and the upper shielding layer  27 .  
         [0129]    While in FIG. 5, the recess  20   a  is formed in the lower shielding layer  20 , and the insulating layer  29  is formed in this recess  20   a , an insulating layer  28  having a slant  28   a  may be formed on the lower shielding layer  20 . It is not always necessary to form the insulating layers  29  and  29  between the lower shielding layer  20  and the electrode layer  25 .  
         [0130]    The manufacturing method of the thin-film magnetic head in the invention will now be described with reference to the drawings. The manufacturing process described below is the manufacturing method of the portion where the multilayer film  23  of the magnetoresistive effect element  22  appears on the cross-section.  
         [0131]    FIGS.  6  to  9  illustrate the processes regarding the first manufacturing method of the thin-film magnetic head of the invention.  
         [0132]    The process shown in FIG. 6 is to form an insulating material layer  31  made of one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4  and AlN on the entire surface of the lower shielding layer  20  into the thickness h 4 .  
         [0133]    Then, as shown in FIG. 7, a resist layer  32  is formed at a certain distance t 1  on the insulating material layer  31 . The distance t 1  is larger than the width of the multilayer film  23  of the magnetoresistive effect element  22  formed in a subsequent step.  
         [0134]    In the process shown in FIG. 8, the insulating material layer  31  not covered with the resist layer is removed by the application of isotropic plasma etching using CF 4  gas or BCl 3  gas. The above-mentioned insulating materials SiO 2 , Ta 2 O 3 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3  and Si 3 N 4  are etchable by isotropic plasma etching of CF 4  gas. By using CF 4  gas, etching never causes a damage to the surface of the lower shielding layer  20 .  
         [0135]    Etching of Al 2 O 3  or AlN is possible with BCl 3  gas. Upon this etching, the surface of the lower shielding layer  20  is also affected by etching. By properly controlling the etching rate and the like, however, the surface of the lower shielding layer  20  is hardly etched.  
         [0136]    Further, by carrying out rinsing after the completion of isotropic plasma etching, corroded portions of the surface of the lower shielding layer  20  are properly removed, thus making it possible to form a pattern of the insulating material layer  31  without causing a damage to the lower shielding layer  20  by etching.  
         [0137]    The insulating material layer  31  remaining under the resist layer  32  shown in FIG. 8 is an insulating layer  33 , and a slant  33   a  is formed on the side of this insulating layer  33  as a result of use of the isotropic etching.  
         [0138]    As shown in FIG. 9, the lower gap layer  21  is formed on an area covering the insulating layer  33  and the lower shielding layer  20  after removing the resist layer  32 . At this point, the total thickness of the thickness h 4  of the insulating layer  33  and the thickness (lower gap length) GL 1  of the lower gap layer  21  should preferably be at least 700 Å.  
         [0139]    Also as shown in FIG. 9, a multilayer film  23  of the magnetoresistive effect element  22  is formed on the lower gap layer  21  not having the insulating layer  33  formed thereon on the lower shielding layer  20 , and the electrode layer  25  of the magnetoresistive effect element  22  is formed on the lower gap layer  21  overlapping the insulating layer  33 , on the lower shielding layer  20 .  
         [0140]    FIGS.  10  to  13  illustrate processes in a second manufacturing method of the thin-film magnetic head of the invention.  
         [0141]    First, in the process shown in FIG. 10, an insulating material layer  34  made of one or more insulating materials selected from the group consisting of SiO 2 , Al 2 O 3 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3 , Si 3 N 4  and AlN is formed on the entire surface of the lower shielding layer  20  into a thickness h 5 .  
         [0142]    Then, as shown in FIG. 10, a resist layer  35  is formed on the insulating material layer  34  at a certain distance t 2 . The distance t 2  is larger than the width of the multilayer film  23  of the magnetoresistive effect element  22  formed in a subsequent process.  
         [0143]    In the process shown in FIG. 11, a heat treatment is applied to the resist layer  35  to produce smearing on the surface of the resist layer  35 , thereby forming a slant  35   a  on the side of the resist layer  35 .  
         [0144]    In the process shown in FIG. 12, the insulating material layer  34  not covered with the resist layer  35  is removed by an anisotropic etching method such as RIE based on CF 4  gas or BCl 3  gas. The above-mentioned insulating materials such as SiO 2 , Ta 2 O 5 , TiO, Ti 2 O 3 , Ti 3 O 5 , WO 3  and Si 3 N 4  are etchable by the anisotropic etching method based on CF 4  gas. By using CF 4  gas, therefore, etching never cause a damage to the surface of the lower shielding layer  20  made of permalloy or the like.  
         [0145]    Al 2 O 3  and AlN are etchable with BCl 3  gas. Upon etching, the lower shielding layer  20  is also affected by etching. By properly controlling the etching rate and the like, however, the surface of the lower shielding layer  20  is hardly etched. Moreover, by applying rinsing after the completion of anisotropic etching (for example, RIE (reactive ion etching method)), corroded portions on the surface of the lower shielding layer  20  are appropriately removed, and it is possible to form a pattern on the insulating material layer  34  without causing any damage to the lower shielding layer  20  by etching.  
         [0146]    The insulating material layer  34  remaining under the resist layer  35  shown in FIG. 12 is an insulating layer  36 , and a slant  36   a  is formed on the side of this insulating layer  36 .  
         [0147]    The reason of formation of the slant  36   a  on the side of the insulating layer  36  is as follows. By forming the slant  35   a  on the side by applying a heat treatment to the resist layer  35  as shown in FIG. 11, the thickness of the portion of the resist layer  35  at the slant  35   a  is reduced, and as a result, the resist layer  35  at the slant  35   a  is ground off under the effect of etching in response to the thickness of the slant  35   a . Therefore, by grinding of the resist layer in response to the thickness of the slant  35   a , the side of the insulating layer  36  formed under the slant  35   a  of the resist layer  35  is also ground off under the effect of etching, thus forming the slant  36   a.    
         [0148]    In the process shown in FIG. 13, the lower gap layer  21  is formed on an area covering the insulating layer  36  and the lower shielding layer  20  after removing the resist layer  35 . At this point, the total thickness of the thickness h 5  of the insulating layer  36  and the thickness (lower gap length) GL 1  of the lower gap layer  21  should preferably be at least 700 Å.  
         [0149]    As shown in FIG. 13, the multilayer film  23  of the magnetoresistive effect element  22  is formed on the lower gap layer  21  not having an insulating layer  36  formed thereon, on the lower shielding layer  20 , and the electrode layer  25  of the magnetoresistive effect element  22  is formed on the lower gap layer  21  overlapping the insulating layer  36 , on the lower shielding layer  20 .  
         [0150]    Further as shown in FIG. 4, when forming the insulating layer  30 , via the upper gap layer  26 , on the electrode layer  25  of the magnetoresistive effect element  22 , it is desirable to use any of the manufacturing method using the anisotropic etching method shown in FIGS.  6  to  9  and the manufacturing method using the isotropic etching method as shown in FIGS.  10  to  13 .  
         [0151]    FIGS.  14  to  17  illustrate processes regarding a third manufacturing method of the thin-film magnetic head of the invention.  
         [0152]    In the process shown in FIG. 14, a lift-off resist layer  37  having a certain width t 3  is formed on the lower shielding layer  20 .  
         [0153]    In the process shown in FIG. 15, the surface of the lower shielding layer  20  not covered with the resist layer  37  is ground of to a depth h 6  by the ion milling method. As a result, a recess  20   a  having a depth h 6  is formed on the surface of the lower shielding layer  20 .  
         [0154]    In the process shown in FIG. 16, an insulating layer  38  is formed, by sputtering or the ion beam depositing method such as ion beam sputtering, in the recess  20   a  formed on the surface of the lower shielding layer  20 . At this point, the surface of the insulating layer  38  should preferably be flush with the surface of the lower shielding layer  20 .  
         [0155]    The insulating layer  38  may be made of any insulating material.  
         [0156]    As shown in FIG. 16, an insulating material layer  39  is formed also on the resist layer  37  by forming the insulating layer  38  in the recess  20   a  formed on the surface of the lower shielding layer  20  by sputtering or by the ion beam deposition method such as ion beam sputtering.  
         [0157]    In the process shown in FIG. 17, the resist layer  37  is removed by lifting off, and the lower gap layer  21  is formed on the surface of the lower shielding layer  20  from the surface of the insulating layer  38 . At this point, the total thickness of the thickness h 6  of the insulating layer  38  and the thickness (lower gap length) GL 1  of the lower gap layer  21  should preferably be at least 700 Å.  
         [0158]    As shown in FIG. 17, the multilayer film  23  of the magnetoresistive effect element  23  is formed on the lower gap layer  21  not having the insulating layer  38  formed thereon, on the lower shielding layer  20 . The electrode layer  25  of the magnetoresistive effect element  22  is formed on the lower gap layer  21  overlapping the insulating layer  38 .  
         [0159]    The electrode  25  of the magnetoresistive effect element  22  is thus formed on the lower gap layer  21  having the insulating layer formed thereon, and after forming the multilayer film  23  on the lower gap layer  21  not having a insulating layer formed thereon, the upper gap layer  26  is formed on the magnetoresistive effect element  22 . Then, an upper shielding layer  27  is then formed on the upper gap layer  26 .  
         [0160]    FIGS.  18  to  20  illustrate processes regarding the fourth manufacturing method of the thin-film magnetic head of the invention. FIGS.  18  to  20  illustrate the processes for forming an insulating layer between the upper shielding layer  27  composing the thin-film magnetic head and the electrode layer  25  of the magnetoresistive effect element  22 .  
         [0161]    In the process shown in FIG. 18, an recess  20   a  is formed on the lower shielding layer  20  by the use of the manufacturing method shown in FIGS.  14  to  16 . After forming an insulating layer  38  in this recess  20   a , the lower gap layer  21  is formed on an area covering the lower shielding layer  20  and the insulating layer  38 . It is not always necessary to form the insulating layer  38 .  
         [0162]    Then, as shown in FIG. 18, the multilayer film  23  is formed on the entire surface of the lower gap layer  21 . Then, a lift-off resist layer  45  is formed on the multilayer film  23 . As shown in FIG. 18, a notch  45   a  is provided on the lower surface of the resist layer  45 .  
         [0163]    In the process shown in FIG. 19, the multilayer film  23  not covered with the lift-off resist layer  45  is removed by etching. As a result, the multilayer film  23  in a prescribed shape remains under the resist layer  45 .  
         [0164]    Then, a hard magnetic bias layer  24  and the electrode layer  25  are laminated in the areas on the both sides of the multilayer film  23  remaining on the lower gap layer  21  shown in FIG. 19 (see FIG. 20).  
         [0165]    Further, as shown in FIG. 20, an insulating layer  40  is formed on the electrode layer  25  formed in areas A on each of the both sides of the multilayer film  23 . The hard magnetic bias layer  24 , the electrode  25  and the insulating  40  are thus continuously formed by the sputtering method or the vapor deposition method in the areas A on the both sides on the lower gap layer  21 . A layer  24   a  of the hard magnetic bias material, a layer  25   a  of the electrode material, and a layer  40   a  of the insulating material are formed also on the lift-off resist layer  45  by the above-mentioned continuous film forming.  
         [0166]    By removing the resist layer  45  shown in FIG. 20, and forming the upper shielding layer  27  via the upper gap layer  26  over the insulating layer  40  and the multilayer film  23 , the thin-film magnetic head as shown in FIG. 5 is completed.  
         [0167]    According to the manufacturing method as described above, it is possible to form the insulating layer  40  on the entire surface of the electrode layer  25  composing the magnetoresistive effect element  22 . As described above, it is possible to form the insulating layer  30  via the upper gap layer  26  on the electrode layer  25  of the magnetoresistive effect element  22 , as shown in FIG. 4, by the manufacturing method shown in FIGS.  6  to  9  or FIGS.  10  to  13 . According to this method, however, the slant  26   a  is formed on the upper gap layer  26  as shown in FIG. 4. It is difficult, from the manufacturing point of view, to form the insulating layer  30  to reach the slant  26   a.    
         [0168]    As shown in FIG. 4, the electrode layer  25  is present under the slant  26   a  of the upper gap layer  26 . It is therefore difficult, by the manufacturing method shown in FIGS.  6  to  9  or FIGS.  10  to  13 , to completely cover the electrode layer  25  with the insulating layer  30 . According to the manufacturing method shown in FIGS.  18  to  20 , however, the insulating layer  40  can be formed continuously by sputtering or vapor deposition on the electrode layer formed on the both sides of the multilayer film  23 , thus making it possible to completely cover the entire electrode layer  25  with the insulating layer  40 , and to maintain a satisfactory electrical insulation between the upper shielding layer  27  and the electrode layer  25 .  
         [0169]    According to the present invention, as described above in detail, it is possible to provide a larger gap between the electrode layer and the shielding layer by forming the gap layer into a small thickness and forming an insulating layer, in addition to the gap layer, between the electrode layer and the shielding layer. Even upon occurrence of defects such as pinholes in the gap layer, or occurrence of smearing during height-making fabrication, it is possible to keep satisfactory electrical insulation between the electrode layer and the shielding layer. At the same time, gap layers of small thicknesses can be formed on and under the multilayer film of the magnetoresistive effect element, thus permitting coping with the tendency toward a higher recording density.  
         [0170]    By adopting a total thickness of the thickness of the insulating layer and the thickness of the gap layer of at least 700 Å, it is possible to maintain a better electrical insulation between the electrode layer and the shielding layer.