Patent Publication Number: US-7718218-B2

Title: Thin-film magnetic head, method of manufacturing the same, head Gimbal assembly, and hard disk drive

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of application Ser. No. 10/912,245, filed Aug. 6, 2004, now U.S. Pat. No. 7,440,229 B2, which in turn claims priority to Provisional Application No. 60/580,368, filed Jun. 18, 2004, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a thin-film magnetic head which performs magnetic recording operation by a perpendicular recording system, a method of manufacturing the same, a head gimbal assembly and hard disk drive. 
     2. Related Background Art 
     Surface recording densities in hard disk drives have improved dramatically in recent years. More particularly, surface recording densities in hard disk drives have recently reached 160-200 Gbytes/platter, and are poised to exceed even this level. At the same time, there has been a demand for improved performance of thin-film magnetic heads. 
     Thin-film magnetic heads are largely classified based on their recording systems, which may be divided into longitudinal recording systems wherein information is recorded in the (longitudinal) direction within the recording surface of the hard disk (recording medium), and perpendicular recording systems wherein the orientation of recording magnetization formed on the hard disk is formed in the perpendicular direction of the recording surface to record data. Of these types of systems, perpendicular recording type thin-film magnetic heads are capable of realizing markedly higher recording density than longitudinal recording systems, while they also are less susceptible to thermal fluctuation of the recorded hard disk, and are therefore more promising than longitudinal recording systems. 
     Conventional perpendicular recording type thin-film magnetic heads are disclosed, for example, in U.S. Pat. No. 6,504,675, U.S. Pat. No. 4,656,546, U.S. Pat. No. 4,672,493 and Japanese Unexamined Patent Publication No. 2004-94997. 
     Incidentally, when thin-film magnetic heads of perpendicular recording systems accomplish recording of data in the inner and outer perimeters of hard disks, the magnetic pole tip situated on the side of the medium-opposing surface (also referred to air bearing surface, or ABS), which opposes the recording medium (hard disk), forms an angle (skew angle) with the data recording track. When the writing performance is high with a perpendicular recording type magnetic head (perpendicular magnetic recording head: hereinafter also referred to as “PMR”), this skew angle is responsible for a problem of side fringe, whereby excess data is recorded between adjacent tracks. When side fringe occurs, it can adversely affect detection of the servo signal, or the S/N ratio of the reproduction waveform. Conventional PMRs therefore have a bevel shape wherein the magnetic pole tip on the ABS side of the main pole gradually narrows in width toward one direction. (In this regard, see Japanese Unexamined Patent Publication No. 2003-242607 and Japanese Unexamined Patent Publication No. 2003-203311.) 
     SUMMARY OF THE INVENTION 
     Conventional PMRs include a thin-film magnetic head  400  having the structure shown in  FIGS. 22(A) , (B) (A) and (B), for example. The thin-film magnetic head  400  comprises a lower yoke layer  402  which is formed on an insulating layer  401 , and a main pole layer  403  which has beveled magnetic pole tip disposed at the ABS  404  side, a write shield layer  406  magnetically connected with the main pole layer  403 , opposite the main pole layer  403  and sandwiching a recording gap layer  405  on the ABS  404  side, and a thin-film coil  407 . The thin-film coil  407  is internally insulated each other by a photoresist  408 , and is wound in a planar spiral fashion around a connecting member  409  which connects the main pole layer  403  and the write shield layer  406 . 
     In the thin-film magnetic head  400 , data recording is accomplished by the recording gap layer  405 . The width W 41  near the thin-film coil  407  at the ABS  404  of the magnetic pole tip constitutes the track width, and the hard disk recording density is determined by this width W 41 . The throat height TH is determined by the distance from the ABS  404  of the write shield layer  406  to the photoresist  408 . 
     On the other hand, PMRs with narrower track widths such as the thin-film magnetic head  400  are desirable for improved recording density. Also, a satisfactory overwrite characteristic is preferred, so that data recorded on the recording medium is not overwritten by other data. Consequently, a structure is preferred wherein the lower yoke layer  402  is as close as possible to the ABS  404 . 
     However, since the thin-film magnetic head  400  has the main pole layer  403  formed after the lower yoke layer  402 , forming the main pole layer  403  with a beveled magnetic pole tip affects the lower yoke layer  402  to produce a neck height (hn) as shown in the drawing, and this has lengthened the narrow portion of the width corresponding to the track width by the degree of the neck height hn, potentially resulting in a shift from the designed length. Therefore, the lower yoke layer  402  must be formed distant from the ABS  404  so that d 1  is 0.1-0.3 μm as shown in the drawing, making it difficult to increase the magnetic charge (also known as magnetic volume) at the location near the ABS  404 . Consequently, in a thin-film magnetic head  400 , there is a problem which achieving a satisfactory overwrite characteristic is difficult. 
     It is an object of the present invention, which has been accomplished in light of the problems described above, to provide a thin-film magnetic head having a structure which allows a satisfactory overwrite characteristic to be achieved, as well as a method of manufacturing the same, a head gimbal assembly and a hard disk drive. 
     In order to solve the aforementioned problems, the invention provides a thin-film magnetic head having a laminated construction comprising a main pole layer having a magnetic pole tip on a side of the medium-opposing surface opposing a recording medium, a write shield layer opposing the magnetic pole tip forming a recording gap layer, on the side of the medium-opposing surface, and a thin-film coil wound around at least a portion of the write shield layer, and comprising an upper yoke pole layer having a larger size than the portion of the main pole layer which is more distant from the medium-opposing surface than the recording gap layer, wherein the upper yoke pole layer is joined to the side of the main pole layer which is near the thin-film coil. 
     The thin-film magnetic head has an upper yoke pole layer, having a larger size than the portion of the main pole layer which is more distant from the medium-opposing surface than the recording gap layer, joined to the side of the main pole layer which is near the thin-film coil. 
     In the thin-film magnetic head, the write shield layer may also have a shield tip which opposes the magnetic pole tip on the medium-opposing surface, and formed with the same edge surface height as the upper yoke pole layer. 
     In this thin-film magnetic head, the shield tip absorbs magnetic return from the recording medium. 
     Preferably, the main pole layer and upper yoke pole layer are formed using magnetic materials with different saturated flux densities, and the saturated flux density of the main pole layer is set higher than the saturated flux density of the upper yoke pole layer. 
     This will allow the saturated flux density of the magnetic pole tip to be higher, to avoid saturation of the flux even when the track width of the magnetic pole tip is narrowed. 
     Further, a high tensile strength film made of Ta, W, Mo, TiW, TiN, Cr, NiCr, Mo, Ru or SiN is also preferably provided in contact with the main pole layer. 
     The high tensile strength film can maintain the direction of remnant magnetization of the main pole layer in the direction along the medium-opposing surface after completion of writing. 
     Also, preferably the shield tip and the upper yoke pole layer are formed using magnetic materials with different saturated flux densities, and the saturated flux density of the shield tip is set lower than the saturated flux density of the upper yoke pole layer. 
     In addition, an insulating film by AL-CVD may be formed between the shield tip and the upper yoke pole layer. 
     The upper yoke pole layer may have an enlarged region wherein the lateral width is enlarged at the side near the medium-opposing surface. 
     The invention further provides a method of manufacturing a thin-film magnetic head, wherein a thin-film magnetic head is manufactured by laminating a main pole layer having a magnetic pole tip on a side of the medium-opposing surface opposing the recording medium, a write shield layer opposing the magnetic pole tip forming a recording gap layer, on the side of the medium-opposing surface, and a thin-film coil wound around at least a portion of the write shield layer, the method of manufacturing a thin-film magnetic head comprising the following steps (1) to (5). 
     (1) A step of forming a main pole layer on an insulating layer, in such a manner that it has a magnetic pole tip at the medium-opposing surface side, 
     (2) A step of forming a recording gap layer on the main pole layer, in such a manner that the section at the side distant from the medium-opposing surface of the main pole layer is exposed, 
     (3) A step of forming an upper yoke pole layer having a larger size than the portion of the main pole layer which is more distant from the medium-opposing surface than the recording gap layer, joined with the location not covered by the recording gap layer of the main pole layer, and a shield tip opposing the magnetic pole tip on the medium-opposing surface, in such a manner that the edge surfaces of each are the same height, 
     (4) A step of forming a thin-film coil in such a manner as to contact the upper yoke pole layer via the insulating film, and 
     (5) A step of forming a magnetic shield layer in connection with the shield tip and in connection with the upper yoke pole layer at the side distant from the medium-opposing surface, and forming the write shield layer comprising the magnetic shield layer and the shield tip. 
     By carrying out each of these steps, it is possible to obtain a thin-film magnetic head wherein the upper yoke pole layer having a larger size than the portion of the main pole layer which is more distant from the medium-opposing surface than the recording gap layer is joined to the main pole layer. 
     There may also be included a step of forming a high tensile strength film between the main pole layer and the insulating layer. 
     This will allow manufacture of a thin-film magnetic head having a high tensile strength film in contact with the main pole layer. 
     The method of manufacturing a thin-film magnetic head as described above may further include a step of subjecting the surface of the main pole layer to annealing. 
     By carrying out annealing, it is possible to reduce the effect of remnant magnetization inside the main pole layer after completion of writing. 
     The invention still further provides a head gimbal assembly comprising a thin-film magnetic head formed on a support and a gimbal securing the support, wherein the thin-film magnetic head has a laminated construction comprising a main pole layer having a magnetic pole tip on a side of the medium-opposing surface opposing a recording medium; a write shield layer opposing the magnetic pole tip forming a recording gap layer, on the side of the medium-opposing surface, and a thin-film coil wound around at least a portion of the write shield layer, and comprising an upper yoke pole layer having a larger size than the portion of the main pole layer which is more distant from the medium-opposing surface than the recording gap layer, wherein the upper yoke pole layer is joined at the side of the main pole layer which is near the thin-film coil. 
     The invention still further provides a hard disk device comprising a head gimbal assembly having a thin-film magnetic head and a recording medium opposing the thin-film recording head, wherein the thin-film magnetic head has a laminated construction comprising a main pole layer having a magnetic pole tip on a side of a medium-opposing surface opposing a recording medium, a write shield layer opposing the magnetic pole tip forming a recording gap layer, on the side of the medium-opposing surface, and a thin-film coil wound around at least a portion of the write shield layer, and comprising an upper yoke pole layer having a larger size than the portion of the main pole layer which is more distant from the medium-opposing surface than the recording gap layer, wherein the upper yoke pole layer is joined to the side of the main pole layer which is near the thin-film coil. 
     The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1(A)  is a cross-sectional view of a thin-film magnetic head according to a first embodiment of the invention, in the direction crossing the thin-film coil, and  FIG. 1(B)  is a front view showing the ABS. 
         FIG. 2  is a plan view showing the main pole layer, upper yoke pole layer and write shield layer of a thin-film magnetic head. 
         FIG. 3  is a perspective view showing the portion of the main pole layer joined to the upper yoke pole layer. 
         FIG. 4(A)  and  FIG. 4(B)  are cross-sectional views, corresponding to  FIGS. 1(A)  and (B), for a step of manufacturing a thin-film magnetic head according to the first embodiment. 
         FIGS. 5(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 4(A)  and (B), respectively. 
         FIGS. 6(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 5(A)  and (B), respectively. 
         FIGS. 7(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 6(A)  and (B), respectively. 
         FIGS. 8(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 7(A)  and (B), respectively. 
         FIG. 9(A)  is a cross-sectional view of a thin-film magnetic head according to a second embodiment of the invention, in the direction crossing the thin-film coil, and  FIG. 9(B)  is a front view showing the ABS. 
         FIGS. 10(A)  and (B) are cross-sectional views, corresponding to  FIGS. 9(A)  and (B), for a step of manufacturing a thin-film magnetic head according to the second embodiment. 
         FIGS. 11(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 10(A)  and (B), respectively. 
         FIGS. 12(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 11(A)  and (B), respectively. 
         FIGS. 13(A)  and (B) are cross-sectional views showing the steps subsequent to  FIGS. 12(A)  and (B), respectively. 
         FIGS. 14(A)  and (B) are illustrations showing a modification to the thin-film magnetic head of the first embodiment of the invention, wherein  FIG. 14(A)  is a cross-sectional view and  FIG. 14(B)  is a front view showing the ABS. 
         FIGS. 15(A)  and (B) are illustrations showing another modification to the thin-film magnetic head of the first embodiment of the invention, wherein  FIG. 15(A)  is a cross-sectional view and  FIG. 15(B)  is a front view showing the ABS. 
         FIGS. 16(A)  and (B) are illustrations showing a modification to the thin-film magnetic head of the first embodiment of the invention, wherein  FIG. 16(A)  is a cross-sectional view and  FIG. 16(B)  is a front view showing the ABS.  FIG. 16(C)  is a plan view showing the main pole layer and upper yoke pole layer, together with the direction of internal magnetization. 
         FIG. 17  is a cross-sectional view of a thin-film magnetic head according to a third embodiment of the invention, in the direction crossing the thin-film coil. 
         FIG. 18  is a cross-sectional view, corresponding to  FIG. 17 , for a step of manufacturing a thin-film magnetic head according to the third embodiment. 
         FIG. 19  is a cross-sectional view showing the step subsequent to  FIG. 18 . 
         FIG. 20  is a plan view showing the main pole layer of a thin-film magnetic head, and a different upper yoke pole layer and write shield layer. 
         FIG. 21  is a perspective view of a hard disk drive provided with a thin-film magnetic head according to the first embodiment of the invention. 
         FIGS. 22(A)  and (B) are illustrations of a conventional thin-film magnetic head, wherein  FIG. 22(A)  is a cross-sectional view and  FIG. 22(B)  is a front view showing the ABS. 
     
    
    
     DETAILED DESCRIPTION OF THE REFERRED EMBODIMENTS 
     Embodiments of the present invention will now be explained in greater detail with reference to the accompanying drawings. Constituents identical to each other will be referred to with numerals identical to each other without repeating their overlapping explanations. 
     First Embodiment 
     (Structure of Thin-film Magnetic Head) 
     The structure of a thin-film magnetic head according to the first embodiment of the invention will be explained first, with reference to  FIGS. 1 to 3 .  FIG. 1(A)  is a cross-sectional view of a thin-film magnetic head  300  according to a first embodiment of the invention, in the direction crossing the thin-film coil, and  FIG. 1(B)  is a front view showing the ABS,  FIG. 2  is a plan view showing the main pole layer  10 , upper yoke pole layer  20  and first shield section  41  of the thin-film magnetic head  300 , and  FIG. 3  is a perspective view showing the joining portion of the main pole layer  10  and the upper yoke pole layer  20 . 
     The thin-film magnetic head  300  according to the first embodiment is a perpendicular recording type magnetic head having an ABS  30  as the medium-opposing surface opposing the recording medium (hard disk), and it comprises a substrate, a reproduction head with an MR element (magnetoresistance effect element), etc. laminated on the substrate, and recording head.  FIGS. 1(A)  and (B) show the recording head laminated on an insulating layer  1 , but the substrate and reproduction head are not shown. The construction of the essential parts of the thin-film magnetic head  300  is explained below, while the construction of the other parts will be explained afterwards in connection with the manufacturing steps. 
     The recording head comprises a main pole layer  10 , an upper yoke pole layer  20 , a recording gap layer  24 , a write shield layer  40  and a thin-film coil  100 , and is constructed with these elements laminated on the insulating layer  1  on the substrate, which is not shown. 
     The main pole layer  10  has a magnetic pole tip  11  and a yoke section  12 . The main pole layer  10  has a narrow track width structure wherein the lateral width W 1  of the pole tip  11  described hereunder is narrowed, in order to give the thin-film magnetic head  300  a high data recording density, and a magnetic material (Hi-Bs material) with a higher saturated flux density than the upper yoke pole layer  20  is used so that the flux will not be saturated even with a narrowed track width structure (this will be described in detail hereunder). 
     The magnetic pole tip  11  is situated at the ABS  30  side, and comprises a track width specifier with a fixed width which specifies the track width. As shown in  FIG. 1B , the magnetic pole tip  11  at the ABS  30  has a lateral width W 1  near the thin-film coil  100  in the direction along the ABS  30  and a lateral width W 2  distant from the thin-film coil  100 , and has a beveled shape such that its lateral width gradually narrows with the distance from the thin-film coil  100  (W 1 &gt;W 2 , where the lateral width W 1  is the track width). The depth of the magnetic pole tip  11  (the distance from the ABS  30 ) corresponds to the throat height TH. (For this embodiment, the throat height TH is about 0.1-0.3 μm, and preferably 0.2 μm.) 
     The yoke section  12  is the section of the main pole layer  10  which is more distant from the ABS  30  than the recording gap layer  24 , and it is situated at a location more distant from the ABS  30  than the magnetic pole tip  11 . The yoke section  12  has a variable width region wherein the width gradually widens with increasing distance from the ABS  30  and a fixed width region whose width is fixed, and the upper yoke pole layer  20  is joined to the surface at the side near the thin-film coil  100 . 
     The upper yoke pole layer  20  is situated at a position distant from the ABS  30  by a depth D (about 0.5-1.0 μm) and comprises a variable width region  21  wherein the lateral width gradually widens with increasing distance from the ABS  30  and a fixed width region  22  which having a fixed lateral width, and its overall size (area) is larger than the size of the yoke section  12 . Also, the upper yoke pole layer  20  is joined to the surface of the yoke section  12  at the side near the thin-film coil  10 , so that the yoke section  12  is housed internally. That is, the upper yoke pole layer  20  is joined to the yoke section  12  in such a manner that the peripheral section is situated outward from the yoke section  12 . The lateral width W 3  of the section protruding outward from the yoke section  12  is approximately 0.5 μm. 
     Also, the upper yoke pole layer  20  is magnetically connected with the write shield layer  40  at the section distant from the ABS  30 , forming a link section  44  with the write shield layer  40 . 
     The recording gap layer  24  is formed between the main pole layer  10  and the first shield section  41  (described hereunder) of the write shield layer  40 . 
     The write shield layer  40  has a first shield section  41 , a second shield section  42  and a third shield section  43 . The first shield section  41  is the shield tip according to the invention, and it is formed opposing the magnetic pole tip  11  of the main pole layer  10  via the recording gap layer  24 , with the throat height TH determined by the depth in the direction crossing the ABS  30  (see  FIG. 2 ). Also, the first shield section  41  has an edge surface  41   a  which is formed to the same height as the edge surface  20   a  at the side of the upper yoke pole layer  20  near the thin-film coil  100  (see  FIG. 2 ), and the second shield section  42  is connected to this edge surface  41   a.    
     The second shield section  42  is formed in connection with the first shield section  41  and the upper yoke pole layer  20  from the side near the thin-film coil  100 , and has a height equal to the thickness of the thin-film coil  100 . The third shield section  43  is formed in connection with the second shield section  42 , covering the thin-film coil  100  and photoresist  101  via the insulating layer  32 . 
     The thin-film coil  100  is wound in a planar spiral fashion around the second shield section  42 , while insulated with respect to the upper yoke pole layer  20  and write shield layer  40  via the respective insulating layers  31 ,  32 . 
     The thin-film magnetic head  300  having the construction described above has the upper yoke pole layer  20  joined to the surface at the side of the main pole layer  10  near the thin-film coil  100 , and it is formed after the main pole layer  10  (described in detail hereunder). Consequently, since the magnetic pole tip  11  is already formed before the upper yoke pole layer  20 , the upper yoke pole layer  20  is not affected by the step of forming the magnetic pole tip  11 , and therefore its shape undergoes no change. As a result, the length of the section of narrow width having the track width is determined by the magnetic pole tip  11  and does not deviate from the designed length, so that the length may be set as projected. The upper yoke pole layer  20  can therefore be formed near the ABS  30 . In addition, the upper yoke pole layer  20  has a larger size than the yoke section  12  of the main pole layer  10 , and its magnetic charge (also known as magnetic volume) is also greater. 
     Consequently, the thin-film magnetic head  300  may have the upper yoke pole layer  20 , which has a greater magnetic charge, situated near the ABS  30 , in order to increase the magnetic charge near the ABS  30 . As a result, the thin-film magnetic head  300  has a construction which permits a satisfactory overwrite characteristic. 
     The thin-film magnetic head  300  also has a first shield section  41  wherein the upper yoke pole layer  20  and edge face are formed to the same height, and the first shield section  41  is situated so as to oppose the magnetic tip  11  via the recording gap layer  24  at the ABS  30 . This first shield section  41  can absorb magnetic return from the recording medium, to thus prevent leakage of excess magnetism. This allows a satisfactory overwrite characteristic to be maintained even when the upper yoke pole layer  20  is formed near the ABS  30 , in order to prevent ATE (Adjacent Track Erase). 
     In order to increase the data recording density, the lateral width W 1  of the magnetic pole tip  11  is narrowed to create a narrow track width structure, and the main magnetic pole  10  is formed using a magnetic material with a higher saturated flux density than the upper yoke pole layer  20  so that the flux is not saturated. 
     This will now be explained with reference to  FIGS. 16(A) , (B) and (C).  FIGS. 16(A)  and (B) are cross-sectional and front views of thin-film magnetic heads  303 ,  304  manufactured by steps different than for the thin-film magnetic head  300 , and  FIG. 16(C)  is a plan view showing the main pole layer  10  and upper yoke pole layer  20 , together with the direction of internal magnetization. The thin-film magnetic heads  303 ,  304  differ from the thin-film magnetic heads  301 ,  302  described hereunder in the sizes of the recording gap layer  24 . 
     In the main pole layer  10 , the saturated flux density of the magnetic material is higher than the saturated flux density of the upper yoke pole layer  20 , and therefore it is difficult to reduce the magnetostriction λ. Consequently, even if the direction of magnetization ms is aligned along the direction ABS  30 , the orientation of the remnant magnetization mr of the main pole layer  10  after completion of writing is toward the ABS  30  side and therefore tends to be oriented in another direction which is different from the direction along the ABS. 
     In the thin-film magnetic head  300 , however, since a magnetic material having a lower saturated flux density than the main pole layer  10  can be used for the upper yoke pole layer  20  to reduce the magnetostriction λ, the direction of remnant magnetization of the upper yoke pole layer  20  after completion of writing may be prevented from being directed in the another direction. 
     Also, since the upper yoke pole layer  20  is joined to the main pole layer  10 , the direction of remnant magnetization mr of the main pole layer  10  after completion of writing is corrected by the magnetization of the upper yoke pole layer  20 , and to be prevented from being directed in the another direction as shown in  FIG. 16(C) . 
     In other words, by joining the upper yoke pole layer  20  with the main pole layer  10 , the direction of remnant magnetization mr of the main pole layer  10  after completion of writing is corrected by the magnetization of the upper yoke pole layer  20 . Hence, there is no erasure of data already written on the hard disk by leakage flux due to remnant magnetization mr. The thin-film magnetic head  300  can therefore effectively prevent appearance of pole erasure while improving recording density. Pole erasure is the phenomenon wherein, after data has been written on a recording medium (hard disk) having a high maximum coercivity Hc, leakage flux flows from the ABS to the hard disk, even in the absence of a write current flow to the thin-film coil, thus erasing other data. 
     (Method of Manufacturing Thin-film Magnetic Head) 
     A method of manufacturing the thin-film magnetic head  300  according to the first embodiment having the construction described above will now be explained with reference to  FIGS. 1(A) , (B) to  FIG. 3  and  FIGS. 4(A) , (B) to  FIGS. 8(A) , (B) 
       FIGS. 4(A) , (B) to  FIGS. 8(A) , (B) show cross-sectional views of manufacturing steps corresponding to  FIGS. 1(A) , (B), respectively. 
     In the manufacturing method of this embodiment, first a reproduction head provided with an MR element (magnetoresistance effect element), etc. is laminated on a substrate (not shown) made of, for example, aluminum oxide/titanium carbide (Al 2 O 3 .TiC), and an insulating layer  1  separating the reproduction head and recording head is formed to a thickness of, for example, about 0.2-0.3 μm. 
     Next, the insulating layer  1  is coated with a photoresist and a prescribed photomask is used for patterning to form a resist pattern with a taper angle of 7-10° on the ABS  30 . The resist pattern is used for plating with CoFe or CoNiFe as the magnetic material having a high saturated flux density of 2.3 T-2.4 T to a thickness of about 0.6-0.8 μm, to form a main pole layer  10  having a magnetic pole tip  11  at the ABS  30  side. The electrode film (not shown) formed for the plating is then removed, leaving the condition shown in  FIGS. 4(A) , (B). The plating is carried out to a thickness of about 0.7 μm. 
     Next, an insulating section  33  made of alumina (Al 2 O 3 ) is formed to a thickness of, for example, 0.5-1.0 μm on the entire surface of the laminated body, and the surface is polished by chemical mechanical polishing (hereinafter “CMP”) so that height (insulating section  33  thickness) of main pole layer  10  become about 0.2-0.25 μm, as shown in  FIG. 5(A) , (B), for surface flattening treatment. This results in the condition shown in  FIG. 5(A) , (B), with the insulating section  33  situated at a location where the main pole layer  10  is absent. 
     Either before or after the polishing by CMP, at least the surface of magnetic pole tip  11  of the main pole layer  10  may be subjected to annealing at 200-260° C. Annealing can reduce the effect of remnant magnetization inside the magnetic pole tip  11  after completion of writing. The annealing is preferably carried out after formation of the recording gap layer  24  described hereunder. 
     Next, a coating is formed over the entire top surface of the laminated body to 400-500 Å, to form a recording gap layer  24 . The material of the coating may be an insulating material such as alumina or the like, or a non-magnetic metal material such as Ru, NiCu, Ta, W, Cr, Al 2 O 3 , Si 2 O 3  or the like. The coating is then selectively etched to leave a region at the ABS  30  side, and expose a section of the side distant from the ABS  30  of the main pole layer  10  (the exposed section serving as the aforementioned yoke section  12 ). This results in formation of a recording gap layer  24  such as shown in  FIG. 6(A) , (B). 
     A plating method is used to form the upper yoke pole layer  20  and the first shield section  41 , in the same step, over the entire surface of the laminated body to a thickness of about 0.3-1.0 μm, using NiFe having a saturated flux density of 1.0-1.6 T or CoNiFe having a saturated flux density of 1.9-2.1 T and a small magnetostriction λ and maximum coercivity Hc as the magnetic material. The upper yoke pole layer  20  is formed so that it is joined to the location of the main pole layer  10  which is not covered with the recording gap layer  24 , and so that the first shield section  41  is in contact with the ABS  30  side of the recording gap layer  24 . The upper yoke pole layer  20  and the first shield section  41  are formed so that their respective edge surfaces have the same height in the subsequent steps. Also, the first shield section  41  is formed at a position which determines the throat height TH, in such a manner as to oppose the magnetic pole tip  11  via the recording gap layer  24  at the ABS  30 . 
     The upper yoke pole layer  20  and first shield section  41  may be formed by a plating method using CoNiFe or NiFe as the magnetic material. A magnetic material such as FeN, FeCoZrO or FeAlN (each magnetic material has a small magnetostriction λ and maximum coercivity Hc and a saturated flux density of 1.9-2.0 T) is used to form a coating by a sputtering method, and the coating may be subjected to reactive ion etching (hereinafter, “RIE”) or ion beam etching (hereinafter, “IBE”). 
     Next, as shown in  FIG. 7(A) , (B), an insulating film  34  made of alumina (Al 2 O 3 ) is formed over the entire surface of the laminated body to a thickness of, for example, 1.0-1.5 μm. The surface is polished by CMP so that thickness of first shield section  41  and upper yoke pole layer  20  is about 0.3-0.8 μm, for surface flattening treatment. The surface flattening treatment produces edge surfaces of the same height for the first shield section  41  and upper yoke pole layer  20 . 
     Next, an insulating film made of alumina (Al 2 O 3 ) is formed over the entire surface of the laminated body to a thickness of about 0.2 μm, and an opening is formed at the locations where the second shield section  42  is to be formed (a location which can be connected to the first shield section  41  and a location which can be connected to the upper yoke pole layer  20 ). This results in an insulating film  31  for insulation so that shorting does not occur between the thin-film coil  100  and the upper yoke pole layer  20 . 
     Next, a frame is formed on the insulating film  31 , using an electrode film (not shown) made of a conductive material and employing photolithography, and then electroplating is carried out using the electrode film to form a plating layer made of Cu. The plating layer and the electrode film below it constitute the thin-film coil  100 . The thin-film coil  100  are formed in contact with the upper yoke pole layer  20  via the insulating film  31 . 
     A frame is then formed by photolithography and a second shield section  42  serving as the magnetic shield layer of the invention is formed by frame plating (not shown). The second shield section  42  is formed using the same magnetic material as for the first shield section  41 . The second shield section  42  and the thin-film coil  100  may also be formed in the facing order. 
     Also, as shown in  FIG. 8(A) , (B), a photoresist  101  is coated to cover the entire surface of the laminated body, and an insulating film made of alumina (Al 2 O 3 ) is formed thereover, after which the entire surface is polished by CMP for flattening treatment of the surface. In this case, the polishing of the surface by CMP is carried out so that the thickness of the thin-film coil  100  and second shield section  42  is about 2.0-2.5 μm. 
     Next, an insulating film made of alumina (Al 2 O 3 ) is formed covering the entire surface of the laminated body, to a thickness of about 0.2 μm, and then an opening is formed at the location where the second shield section  42  is to be formed. This results in an insulating film  32  for insulation so that shorting does not occur between the thin-film coil  100  and the third shield section  43 . 
     When forming the third shield section  43  serving as the magnetic shield layer of the invention, to a thickness of about 2-3 μm, a write shield layer  40  is formed opposing the magnetic pole tip  11  via the recording gap layer  24 , in connection with the upper yoke pole layer  20 , to obtain a thin-film magnetic head  300  as shown in  FIG. 1(A) , (B). The thin-film magnetic head  300  obtained in this manner, having the construction described above, is able to exhibit a satisfactory overwrite characteristic. 
     Modification Example 1 
     The manufacturing steps described above may be modified in the following manner. Specifically, as shown in  FIG. 6(A) , (B), after the first shield section  41  and upper yoke pole layer  20  have been formed, the thin-film coil  100  may be formed via the insulating film  31 , before the second shield section  42 . Next, a photoresist  101  may be formed covering the thin-film coil  100 . The second shield section  42 , serving as the magnetic shield layer of the invention, is then formed covering the photoresist  101 , in connection with the first shield section  41  and the upper yoke pole layer  20 . This yields a thin-film magnetic head  301  including a write shield layer  40  having a first shield section  41  and second shield section  42 , not having a third shield section  43 , as shown in  FIG. 14(A) , (B). 
     This thin-film magnetic head  301  differs from the thin-film magnetic head  300  in that it has no third shield section  43 , but it otherwise has the same construction and exhibits the same function and effect as the thin-film magnetic head  300 . Also, since it does not require a step to manufacture the third shield section  43  in addition to the second shield section  42 , the manufacturing steps can be reduced. 
     Modification Example 2 
     A tensile film  15  may also be provided in connection with the main pole layer  10 , between the insulating layer  1  and the main pole layer  10 , as in the thin-film magnetic head  302  shown in  FIGS. 15(A)  and (B). The tensile film  15  is a high tensile strength film made of Ta, W, Mo, TiW, TiN, Cr, NiCr or the like, and formed with application of a high tensile strength of 200 MPa or greater. By providing the tensile film  15  it is possible to maintain the direction of remnant magnetization mr of the main pole layer  10  after completion of writing in the direction along the ABS  30 . Thus, the thin-film magnetic head  302  can effectively prevent appearance of pole erasure. 
     Modification Example 3 
     Also, as shown in  FIG. 20 , the variable width region  21  of the upper yoke pole layer  20  may be provided with an enlarged region  23  wherein the lateral width is enlarged at the side near the ABS  30  (W 4  shown in  FIG. 20  has a width of about 0.5-3.0 μm). Such provision of the enlarged region  23  in the upper yoke pole layer  20  will allow the magnetic charge of the upper yoke pole layer  20  to be increased near the ABS  30 , so that the overwrite characteristic can be even more satisfactory. 
     Second Embodiment 
     A thin-film magnetic head according to a second embodiment of the invention will now be explained with reference to  FIG. 9(A) , (B).  FIG. 9(A)  is a cross-sectional view of the thin-film magnetic head  310  according to the second embodiment of the invention, in the direction crossing the thin-film coil, and  FIG. 9(B)  is a front view showing the ABS. 
     (Structure of Thin-film Magnetic Head) 
     The thin-film magnetic head  310  according to the second embodiment of the invention differs from the thin-film magnetic head  300  described above primarily in that it has a tensile film  16  similar to the tensile film  15  and in that it has insulating films  35 ,  36  instead of insulating film  34 , but is the same in its other aspects. The differences will now be explained, ignoring the aspects which are identical. 
     The tensile film  16  is formed between the insulating layer  1  and the main pole layer  10 , in contact with the main pole layer  10 . In this thin-film magnetic head  310 , therefore, the tensile film  16  allows the direction of remnant magnetization mr of the main pole layer  10  after completion of writing to be maintained in the direction along the ABS  30 , to effectively prevent appearance of pole erasure. The insulating films  35 ,  36  are formed at a position of the recording gap layer  24  which is more distant from the ABS  30  than the first shield section  41 . 
     Since the thin-film magnetic head  310  having this construction likewise has the same main pole layer  10  and upper yoke pole layer  20  as the thin-film magnetic head  300 , the construction allows the magnetic charge to be increased near the ABS  30 , for a satisfactory overwrite characteristic. 
     In addition, since it has the same first shield section  41  as the thin-film magnetic head  300 , the first shield section  41  can absorb magnetic return from the recording medium, to thus prevent leakage of excess magnetism. This allows a satisfactory overwrite characteristic to be maintained, in order to prevent ATE. 
     (Method of Manufacturing Thin-film Magnetic Head) 
     A method of manufacturing the thin-film magnetic head  310  according to the second embodiment having the construction described above will now be explained with reference to  FIG. 9(A) , (B) and  FIG. 10(A) , (B) to  FIG. 13(A) , (B).  FIG. 10(A) , (B) to  FIG. 13(A) , (B) show cross-sectional views of manufacturing steps corresponding to  FIG. 9(A) , (B), respectively. 
     In this embodiment, similar to the first embodiment, an insulating layer  1  is formed on a substrate (not shown) to a thickness of, for example, about 0.2-0.3 μm. 
     Next, as shown in  FIG. 10(A) , (B), a tensile film  16  is formed to a thickness of 500-1000 Å on the insulating layer  1 . 
     Next, the main pole layer  10  comprising the magnetic pole tip  11  and yoke section  12  is formed by the same procedure as the first embodiment.  FIG. 9(A) , (B) to  FIG. 13(A) , (B) show the shield layer  17  used for plating to form the main pole layer  10  comprising the magnetic pole tip  11  and yoke section  12 . 
     Next, polishing by CMP after formation of the insulating section  33  by the same procedure as the first embodiment produces a state which an insulating section  33  fills in the sections where the main pole layer  10  is absent, as shown in  FIG. 11(A) , (B). In this embodiment as well, annealing is carried out in the same manner as the first embodiment either before or after the polishing by CMP, or after formation of the recording gap layer  24 . 
     Next, as shown in  FIG. 12(A) , (B), the recording gap layer  24 , the first shield section  41  and the upper yoke pole layer  20  are formed by the same procedure as the first embodiment. 
     Also, as shown in  FIG. 13(A) , (B), a coating made of alumina (Al 2 O 3 ) is formed to 1000-3000 Å by AL-CVD, whereby insulating films  35 ,  36  are formed filling in the gap between the first shield section  41  and the upper yoke pole layer  20 . Since the AL-CVD results in satisfactory step coverage, it is possible to form the insulating films  35 ,  36  in such a manner that no keyhole is formed in the narrow space between the first shield section  41  and the upper yoke pole layer  20 . The insulating films  35 ,  36  may also be coated with alumina (Al 2 O 3 ) formed to a thickness of about 0.1-0.5 μm by ALE (Atomic Layer Epitaxy). The alumina (Al 2 O 3 ) insulating films  35 ,  36  are alumina CVD films formed by alternating intermittent injection of H 2 O, N 2  or N 2 O, H 2 O 2  and AL(CH 3 ) 3  or ALCL 3  for forming thin-film, under reduced pressure at a temperature of 180-200° C. 
     Next, the surface of the insulating films  35 ,  36  are polished by CMP to a thickness of about 0.3-0.5 μm, and an opening is formed at the location where the second shield section  42  is to be formed. This yields an insulating film  31 . Also, a thin-film coil  100  and second shield section  42  are formed by the same procedure as for the first embodiment. 
     Also, an insulating film  32  made of alumina (Al 2 O 3 ) is formed thereover to a thickness of 3-4 μm, after which the entire surface is polished by CMP for flattening treatment of the surface. In this case, the polishing of the surface by CMP is carried out so that the thickness of the first shield section  41  and upper yoke pole layer  20  is about 2.0-2.5 μm. The subsequent steps are carried out by the same procedure as for the first embodiment, to obtain a thin-film magnetic head  310  as shown in  FIG. 9(A) , (B). 
     Third Embodiment 
     A thin-film magnetic head according to a third embodiment of the invention will now be explained with reference to  FIG. 17 .  FIG. 17  is a cross-sectional view of the thin-film magnetic head  320  according to the third embodiment of the invention, in the direction crossing the thin-film coil. 
     (Structure of Thin-film Magnetic Head) 
     The thin-film magnetic head  320  according to the third embodiment of the invention differs from the thin-film magnetic head  310  described above primarily in that it has no tensile film  16  and in that the material of the first shield section  41  is different, while it is the same in its other aspects. The differences will now be explained, ignoring the aspects which are identical. 
     In the thin-film magnetic heads  300 ,  310  described above, the upper yoke pole layer  20  and first shield section  41  are formed together in the same step using the same magnetic material, and therefore the saturated flux density of the magnetic material of the first shield section  41  is the same as the saturated flux density of the upper yoke pole layer  20 . 
     However, in order to reduce the effect of remnant magnetization after completion of writing, it is preferred for the saturated flux density of the first shield section  41  formed at the ABS  30  side to be low. The first shield section  41  and upper yoke pole layer  20  are therefore formed using different magnetic materials, so that the saturated flux density of the first shield section  41  is at least lower than the main pole layer  10 , and preferably lower than the upper yoke pole layer  20 . 
     The magnetic material of the first shield section  41  may be NiFe with a saturated flux density of 1.6 T, and NiFe with a saturated flux density of 1.0 T (80%:20%). Alternatively, the magnetic material of the first shield section  41  may be CoNiFe with a saturated flux density of 1.9 T, and CoFe or CoNiFe having a high saturated flux density of 2.3 T-2.4 T as the magnetic material of the main pole layer  10 , while the saturated flux density of the upper yoke pole layer  20  may be the same as, or slightly lower than, the main pole layer  10  (for example, about 1.9 T). 
     (Method of Manufacturing Thin-film Magnetic Head) 
     A method of manufacturing the thin-film magnetic head  320  according to the third embodiment having the construction described above will now be explained with reference to  FIG. 17  above, as well as  FIGS. 18 and 19 . 
     As shown in  FIGS. 18 and 19 , the thin-film magnetic head  320  has a main pole layer  10  and an insulating layer  33  formed, and a recording gap layer  24  formed thereover, in the same manner as the second embodiment. Next, as explained above, a magnetic material with a saturated flux density at least lower than the main pole layer  10  and preferably lower than the upper yoke pole layer  20  (for example, NiFe with a saturated flux density of 1.0 T (80%:20%)) is used to form a first shield section  41  at a position which determines the throat height TH, so that it opposes the magnetic pole section  11  via the recording gap layer  24  at the ABS  30 . 
     Next, as shown in  FIG. 19 , an upper yoke pole layer  20  is formed so that it is joined to the location of the main pole layer  10  which is not covered with the recording gap layer  24 . The remaining steps are carried out in the same manner as for the second embodiment. 
     Incidentally, although the thin-film magnetic head  320  has no tensile film  16 , it may of course have a tensile film  16  and therefore a step may be included of forming a tensile film  16 . At least the surface of the magnetic pole tip  11  of the main pole layer  10  is subjected to annealing. 
     The present invention may also be applied for a record-only head having only an inductive electromagnetic transducer, or it may be applied for a thin-film magnetic head wherein recording and reproduction are accomplished by an inductive electromagnetic transducer. 
     Embodiment of Head Gimbal Assembly and Hard Disk Drive 
     An embodiment of a head gimbal assembly and hard disk drive will now be explained. 
       FIG. 21  is a perspective view showing a hard disk drive  201  comprising the above-mentioned thin-film magnetic head  300 . The hard disk drive  201  comprises a hard disk (recording medium)  202  rotating at a high speed, and a head gimbal assembly (HGA)  215 . The hard disk drive  201  is an apparatus for actuating the HGA  215 , so that magnetic information is recorded onto and reproduced from recording surfaces of the hard disk  202 . The hard disk  202  comprises a plurality of disks (whose number is  3  in the drawing). Each disk has a recording surface opposing the thin-film magnetic head  300 . The HGA  215  comprises a gimbal  212  mounted with a head slider  211  having a support formed with the thin-film magnetic head  300  and a suspension arm  213  for supporting the gimbal  212  which are disposed on the recording surface of each disk, and is rotatable about a shaft  214  by a voice coil motor which is not depicted, for example. As the HGA  215  is rotated, the head slider  211  moves radially of the hard disk  202 , i.e., in directions traversing track lines. 
     Since the HGA  215  and hard disk drive  201  have thin-film magnetic heads  300 , it is possible to achieve a satisfactory overwrite characteristic. An HGA  215  and hard disk drive  201  having thin-film recording heads according to the second and third embodiments can likewise achieve satisfactory overwrite characteristics. 
     It is clear that various embodiments and modified examples of the present invention can be carried out on the basis of the foregoing explanation. Therefore, the present invention can be carried out in modes other than the above-mentioned best modes within the scope equivalent to the following claims.