Abstract:
A thin-film magnetic head comprises a magnetic gap disposed to be positioned on an air bearing surface of the magnetic head, a pair of magnetic poles disposed to hold the magnetic gap therebetween, and a coil positioned between the pair of the magnetic poles to intersect the magnetic poles, wherein at least one of the magnetic poles being composed of a T-shaped magnetic pole, the T-shaped magnetic pole comprising a front part of a magnetic pole contacting with the magnetic gap, an intermediate part of a magnetic pole lying on the front part, and a rear part of a magnetic pole lying on the intermediate part, wherein a width of the front part roughly defines a track width, the rear part has a wider width in a direction of track width than a width of the front part, and the intermediate part contacts with the rear part at an entire width of the rear part at the air bearing surface and has a narrower width at a contacting face with the front part than the width of the rear part.

Description:
This is a continuation in-part application of U.S. Ser. No. 08/626,749, filed Mar. 24, 1997 now U.S. Pat. No. 5,872,693. 
    
    
     BACKGROUND OF THE INVENTION 
     The present application claims priority of Japanese Patent Application No. Hei-9-252481 filed on Sep. 17, 1997. 
     1. Field of the Invention 
     This invention relates to a thin-film magnetic head. 
     2. Description of the Related Art 
     In recent years, the densification of magnetic recording has advanced to a point where systems of such high recording density as 500 Mb/inch 2  in VTR and 200 Mb/inch 2  in HDD have already found acceptance for practical use. Demands for further densification of magnetic recording know no bound. In consequence of the advancing densification of recording, the decrease of track width has become an essential task. The HDD of a recording density of 200 Mb/inch 2 , for example, has sufficiently fulfilled its purpose when the width of a track is 7 μm, the interval between tracks is about 2 μm, and the tolerance of track width is roughly equal to the interval between tracks (2 μm). In order that the HDD may allow further densification of recording, it becomes necessary to decrease the track width to below 5 or 6 μm and the tolerance to below 0.5 μm. Further, it is suspected that the densification of recording to the order of 10 Gb/inch 2 will require the track width to be not more than 1 μm and the tolerance to be in the neighborhood of 0.1 μm. To satisfy these requirements, the magnetic head calls for a distinct improvement. 
     FIG.  11  and FIG. 12 illustrate the construction of a conventional thin-film magnetic head. In these diagrams,  1  denotes a substrate which is formed of such as Al 2 O 3 ·TiC. On this substrate  1 , a first magnetic layer which is made as of Permalloy and destined to serve as a lower magnetic core  3  is superposed through the medium of an insulating layer  2  made as of Al 2 O 3 . On the lower magnetic core  3  are superposed a magnetic gap  4  made as of SiO 2  and an insulating layer  6  made as of polyimide and having embedded therein a coil  5  made as of Cu. On the insulating layer  6 , a second magnetic layer destined to serve as an upper magnetic core  7  is formed. A protective layer  8  made as of Al 2 O 3  is formed on the substrate  1  including the upper side of the upper magnetic core  7 . 
     With respect to the conventional thin-film magnetic head which is provided with such lower magnetic core  3  and such upper magnetic core  7  as are shaped as described above, it has been pointed out that if the width of a track thereof is decreased to the neighborhood of 4 μm, for example, the magnetic head will be at a disadvantage in tending to orient the axis of easy magnetization thereof in the direction perpendicular to the direction of track width, entailing a decline in the permability thereof, and inducing degradation of the head characteristics, particulartly high-frequency response characteristics [“Magnetic Properties of a Narrow-Stripe Cr—Ta—Zr Amorphous Film”, written by Hiroshi Mitsuya et al. and published in the Journal of Japan Applied Magnetics Society, 12, 255-258 (1998)]. 
     The impartation of a track width to the conventional thin-film magnetic head which is constructed as illustrated in FIG.  11  and FIG. 12 is accomplished by selective plating as with Permalloy. In this case, it is the accuracy with which a resist is patterned in the PEP process (photoengravement process) prior to the selective plating that determines the accuracy of the track width. In the case of the thin-film magnetic head, the difference of level h embracing the underlying layers prior to the formation thereon of the upper magnetic core  7  is about 10 μm. In order for this difference of level to be thoroughly covered, the resist requires a thickness equaling this difference of level. For all the possible devices available for coating, the resist requires a thickness of at least about 5 μm. 
     When the exposure is carried out by the contact method, the distance between the surface of a photomask and the bottom surface of the resist is about 15 μm (10 μm difference of level +5 μm thickness of resist) at least. The size of an unfocussed spot (the range in which the intensity of light changes from 100% to 50%) due to the Fresnel diffraction which is attendant on the contact exposure of this nature is found by calculation to be 3.5 μm, an unfitting magnitude even for the density of 200 Mb/inch 2  [interval between tracks (guard band) about 2 μm], let alone the accuracy of track width to be achieved in the distant future. 
     As a solution to this problem, the method of effecting the impartation of a track from the side (ABS layer side) facing the medium has been proposed (IEEE Transaction on Magnetics, Vol. 24, No. 6, November 1988, pp. 2841-2843). Similarly, the method of effecting the impartation of a track from the surface facing the medium by the FIB (focussed ion beam) etching technique has been proposed (refer to JP-A-03-296,907). Though these methods are capable of securing the accuracy of track width as aimed at, they entail a serious problem in terms of the adaptability for mass production because the individual heads on a production line must be processed one by one and because the throughput of FIB&#39;s themselves is unusually poor. 
     Further, the method which aims to narrow the tolerance of processing by forming the upper magnetic core  7  in the form of the combination of a front body  7   a  vested with the general appearance of a fan with a rear body  7   b  extended as far as the rear gap part and shaping the leading half part by the ion beam milling technique in the early stage of manufacture in which the difference of level across the underlying layers is relatively small has been proposed (IEEE Transaction on Magnetics, Vol. 27, No. 6, November 1991, pp.4936-4938). So long as the front body  7   a  of the upper magnetic core  7  is fabricated by the ion beam milling technique, however, the difference between the size of the resist mask and that of the finished magnetic core is inevitably large and is hardly fit for the density of 10 Gb/inch 2 . So long as this method relies for the shaping in question on the ion beam milling technique, it cannot contribute to enhance the productivity because the rate of the milling work is as low as some tens of nm/min. Further, when the ion beam milling-technique involves the introduction of a fluorine type gas, the method suffers from a marked decline of productivity because various deposits occur inside the ion beam gun and prevent the gun from being stably used for a long time. 
     The method which resides in utilizing a selective plating technique for the formation of the front body  7   a  in the general shape of a fan has been also known. So long as the selective plating technique is used, however, the thickness of the resist mask and the difference of level h′ do not deserve to be disregarded. Since the resist must be patterned at least in a depth closely approximating the total thickness (about 6 μm) of the lower and the upper magnetic core, the tolerance of the accuracy of patterning of the resist itself is inevitably enlarged. Besides, very minute portions of the front body  7   a  are given the desired selective plating only with difficulty. 
     In any of the methods described above, the width of the upper and the lower magnetic core opposed to each other across the gap (the upper and lower pole width) cannot be completely equalized because the alignment error occurring between the upper and the lower magnetic core demands due respect and, therefore, the upper magnetic core must be decreased from the lower magnetic core by a margin roughly twice as large as the alignment error. Even in the absence of misalignment, the problem of possibly aggravating the burden of side righting will ensue. 
     As described above, the construction of the thin-film magnetic head and the technique for the impartation of a track to the magnetic head which have been known to the art to date are hardly fit for such accuracy of track width as 10 Gb/inch 2  because they have limits of their own in narrowing the interval between tracks. Thus, the art has not yet realized a thin-film magnetic head of a narrow track interval which satisfies both the requirements regarding dimensional tolerance and adaptability for mass production. The desirability of improving the existing thin-film magnetic head, therefore, has been finding enthusiastic recognition. 
     SUMMARY OF THE INVENTION 
     This invention has been produced for the purpose of solving the problems mentioned above. An object of this invention is to provide a thin-film magnetic head which permits a narrow track fit for the accuracy of up to 10 Gb/inch 2  to be formed thereon while satisfying both dimensional tolerance and adaptability for mass production. 
     The first thin-film magnetic head of the present invention comprises a lower magnetic core formed on a substrate, an upper magnetic core formed on the lower magnetic core with the medium of magnetic gap therebetween, and a coil interposed between the lower magnetic core and the upper magnetic core as insulated from the lower magnetic core and the upper magnetic core, and is characterized in that at least either of the lower magnetic core and the upper magnetic core comprises a front body of a magnetic pole facing a magnetic recording medium and a rear body of the magnetic pole having part thereof superposed on the front body of the magnetic pole, the rear body of the magnetic pole is disposed as recessed from the head surface facing the magnetic recording medium and held in contact with the front body of the magnetic pole in a plane, and the plane is terminated at a rear of the end of the front body of the magnetic pole, and the rear body of the magnetic pole having a shape curved or bent in the direction opposite to the magnetic gap. 
     The second thin-film magnetic head of the present invention comprises a lower magnetic core formed on a substrate, an upper magnetic core formed on the lower magnetic core with the medium of magnetic gap therebetween, and a coil interposed between the lower magnetic core and the upper magnetic core as insulated from the lower magnetic core and the upper magnetic care, and is characterized in that at least either of the lower magnetic core and the upper magnetic core comprises a front body of a magnetic pole facing a magnetic recording medium and a rear body of the magnetic pole having part thereof superposed on the front body of a magnetic pole, and the front body of the magnetic pole is disposed on the same plane as at least part of the remainder of the choice between the lower magnetic core and the upper magnetic core. 
     In the first and the second thin-film magnetic head of the present invention mentioned above, the front body of the magnetic pole may be made of a magnetic material different from that of the rear body of the magnetic pole. For example, the front body of the magnetic pole may be made of a magnetic material having a small anisotropic magnetic field and the rear body of the magnetic pole may be made of a magnetic material having a large anisotropic magnetic field, thereby magnetic properties thereof being improved. 
     Further, in the first and second thin-film magnetic head of the present invention, the front body of the magnetic pole has a laminated construction having a nonmagentic layer interposed between a plurality of magnetic layers. 
     Further in the first and the second thin-film magnetic head of the present invention mentioned above, the front body of the magnetic pole is formed of a magnetic material embedded by collimation sputter in a trench formed in advance in part of an insulation layer. 
     The outer edges of the bottom surface of the magnetic member embedded in the trench or the upper outer edges of the lateral walls of the trench are chamfered. 
     Furthermore, in the first and second thin-film magnetic head of the present invention, the front body of the magnetic pole has the shape of a substantially rectangular solid. 
     The third thin-film magnetic head of the present invention comprises a lower magnetic core formed on a substrate, an upper magnetic core formed on the lower magnetic core with the medium of magnetic gap therebetween, and a coil interposed between the lower magnetic core and the upper magnetic core as insulated from the lower magnetic core and the upper magnetic core, and is characterized in that at least either of the lower magnetic core and the upper magnetic core comprises a front body of a magnetic pole racing a magnetic recording medium and a rear body of a magnetic pole having part thereof superposed on the front body of the magnetic pole and forms on the substrate a projection having a substantially convex shape wherein the rear body of the magnetic pole is connected at an angle of connection in the range of from 90 to 120 degrees to the front body of the magnetic pole. 
     In the above, the front body of the magnetic pole may be made of a magnetic material different from that of the rear body of the magnetic pole. For example, the front body of the magnetic pole has a small anisotropic magnetic field constant and the rear body of the magnetic pole has a large anisotropic magnetic field constant. Further the third thin-film magnetic head can also be improved by using a laminated construction having a non-magnetic layer interposed between a plurality of magnetic layers. 
     The third thin-film magnetic head mentioned above is further characterized in that the front body of the magnetic pole and the rear body of the magnetic pole are formed of magnetic materials embedded by collimation sputter by the use of a collimator of the shape of an orifice in the trench formed in advance in part of an insulating layer and also that the trench mentioned above is tapered with a smaller angle near the bottom parts of the lateral walls defining the trench than at the remaining parts of the lateral walls and is substantially provided with a taper of at least two steps. 
     Further, the thin-film magnetic head mentioned above, where the front part of the magnetic pole of the upper magnetic core and the front part of the magnetic pole of the lower magnetic core are both embedded, is characterized in that the trench for embedding the front part of the magnetic pole of the upper magnetic core is tapered with a smaller angle near the upper parts of the lateral walls defining the trench than at the remaining parts of the lateral walls and the trench for embedding the front part of the magnetic pole of the lower magnetic core is tapered with a smaller angle near the bottom parts of the lateral walls defining the trench than at the remaining parts of the lateral walls. 
     In the thin-film magnetic head of this invention, at least either of the lower magnetic core and the upper magnetic core is composed of a front body of the magnetic pole and a rear body of the magnetic pole held in contact with the front body of the magnetic pole in a plane. Thus, the thin-film magnetic head having a relatively low magnetic resistance at the contact portion, a uniform magnetic flux in the magnetic gap, uniform properties, and high repeatability and ease of manufacture can be easily produced. Further, a front body of the magnetic pole of at least either of the lower magnetic core and the upper magnetic core which are composed of the front body of the magnetic pole and the rear body of the magnetic pole is disposed on the same plane as at least part of the remainder of the choice between the lower magnetic core and the upper magnetic core. Thus, it become possible to deposit the magnetic material and simultaneously form those bodies, thereby the manufacturing process being simple. Further, in the thin-film magnetic head, the trench intended as the site for the formation of the front body of the magnetic pole can be fabricated with high accuracy because this trench is fabricated in a state perfectly free from any difference of level. It also contributes greatly to improve the accuracy of location of the front body of the magnetic pole because this front body of the magnetic pole having the shape of a substantially rectangular solid is formed by embedding a magnetic material by collimation sputter and the like by the use of a collimator of the shape of an orifice in the trench of the description given above. Further, the leading half part of the magnetic pole can be produced in high quality without entrapping any void. Owing to these features, the thin-film magnetic head permits highly accurate impartation thereto of a narrow track endowed with an extremely small tolerance. 
     This invention allows the front body of the magnetic pole and the rear body of the magnetic pole to be formed of mutually different magnetic materials. 
     For example, in case that to be faced and axis of easy magnetization to the track width direction is difficult due to a narrow track such as a track width of about 1 μm, this problem is solved by using a low HK magnetic material having a small anisotropic magnetic field constant as the material of the front body and a higher HK magnetic material having higher permeability in a high frequency region, preferably high resistant material as the material of the rear body. Particularly, the use of the above materials is effective in case of making the front body of the magnetic pole only by the embedding method. This is because when it is embedded the magnetic deterioration due to the disorder of crystal orientation is small in case of using the low HK material. 
     On the other hand, in case that to be faced an axis of easy magnetization to the track width direction is easy due to the process of a wider track, a magnetic material having a higher saturation magnetic flux density or a higher induced magnetic anisotropy may be used. 
     By having the rear body of the magnetic pole disposed as recessed from the face opposite the medium, the occurrence of leakage at the surface opposed to the medium of magnetic flux near the joint between the front body of the magnetic pole and the rear body of the magnetic pole at which the magnetic path assumes a nearly rectangular-bent structure can be precluded and, as a consequence, the accidental recording or regeneration due to the leakage of magnetic flux can be prevented. Further by having the rear body of the magnetic pole so superposed that it may form surface contact with the front body of the magnetic pole and even the rear end part thereof, the efficiency of the head and the noise such as of wiggle can be prevented from being adversely affected by a slight deviation to the head-depth direction of the site for the formation of the rear body of the magnetic pole. Since a polyimide type organic insulating material which does not exhibit very high patterning accuracy can be used in the place of a resist material as in the insulating layer for the coil, a magnetic material which has such a high saturation flux density as requires an annealing treatment to be performed at a temperature of about 350° C. is allowed to be used. 
     In the third thin-film magnetic head of the present invention, the project plane of either of the lower magnetic core or the upper magnetic core on the substrate, as shown in FIG. 15, has a nearly convex shape which is composed of a protuberant front body t of the magnetic pole connected to a rear body r of the magnetic pole at an angle (denoted by θ in the diagram) in the range of from 90 to 120 degrees. Thus, the axis of easy magnetization of the head can be stably paralleled to the direction of the track width even when the track width is decreased. 
     In the magnetic core which is shaped as shown in FIG. 15, the magnetic moment in the rear body r of the magnetic pole tends to assume its course along each side of the core as indicated by an arrow X. The axis of easy magnetization in the front body t of the magnetic pole which has undergone the decrease of track width is susceptible of the influence of the magnetic moment (indicated by a broke-line arrow X 1  in the diagram) directly connected to the superposed region of front body t of the magnetic pole and the rear body r of the magnetic pole. 
     Here, in the third thin-film magnetic head of the present invention, since the part of the magnetic moment X 1  which is exerted on the axis of easy magnetization of the front body t of the magnetic pole in the rear body r of the magnetic pole is caused to assume its course in the direction of the track width by restricting the angle of connection θ between the front body t of the magnetic pole and the rear body r of the magnetic pole within the range of from 90 to 120 degrees, the axis of easy magnetization (indicated by an arrow Y in the diagram) in the front body t of the magnetic pole which has undergone the decrease of track width can be directed to the track width. As a result, the thin-film magnetic head excelling in head characteristics, particularly in the high-frequency response characteristic, can be easily obtained with high repeatability. In contrast thereto, the conventional magnetic core which, as shown in FIG. 16, expands from a front part t′ of the magnetic pole to a rear part r′ of the magnetic pole after the fashion of a fan θ&gt;120 degrees), the magnetic moment of the front part t′ of the magnetic pole tends to assume its course perpendicularly to the direction of its protuberance and the direction of track width as shown by an arrow Y in the diagram under the influence of the magnetic moment of the part directly connected to the front part t′ of the magnetic pole in the rear part r′ of the magnetic pole. As a natural consequence, the axis of easy magnetization of the front part t′ of the magnetic pole inevitably assumes its course perpendicularly to the direction of the track width. 
     Further, in case that at least a magnetic core is formed as a structure in which the front body of the magnetic pole and the rear body of the magnetic pole are formed in a laminated structure, the projected plane thereof on the substrate has also a nearly convex shape (90≦θ≦120), but the effects mentioned above are more remarkable than the magnetic core in which the front part t′ of the magnetic pole and the rear part r′ of the magnetic pole are disposed on the same plane. 
     We will explain the reasons thereof as follows: 
     Conventionally, since magnetization in a soft magnetic member decreases its self-energy, magnetization in the periphery become in parallel with the surface of periphery, as shown in FIG.  17 . When the magnetic member having a size of about 50 μm width×50 μm length×2 μm thickness, the magnetization exhibits a circulating magnetic domain structure. In this case, the axis of easy magnetization is in the direction of the track width. 
     On the other hand, the magnetic member having a size of about 2 μm width×5 μm length×2 μm thickness as the front body of the magnetic pole of the present invention does not exhibit a distinct magnetic domain structure, and occurs the curling of magnetization, as shown in FIG.  18 . Nevertheless, the magnetization of the periphery become in parallel with the surface of the periphery because of decreasing the self demagnetization field energy, as shown in FIG.  18 . 
     When superposing the rear body of the magnetic pole as shown in FIG. 17 on such front body of the magnetic pole and performing switched connecting the planes to be bond, as shown in FIG. 19, the magnetization in the connecting portion of the front body of the magnetic pole turns to the direction of the nearly track width because of affecting by the magnetization in the rear body of the magnetic pole. Accordingly, all magnetization in the front body of the magnetic pole can be turned to the direction of the track width on the whole. As a condition to obtain the above state, the effect becomes larger as the ratio (L 2 /L 1  in FIG. 19) of the superposed portion in the front body of the magnetic pole increases. Further the effect can be obtained when the connecting angle θ between the front body of the magnetic pole and the rear body of the magnetic pole is in the range of about 90 to 120 degrees. Namely, the superposed structure of the front body of the magnetic pole and the rear body of the magnetic pole enables to more easily turn the axis of easy magnetization of the front part of the magnetic pole to the direction of the track width compared with the magnetic pole having no superposed portion even if the projected plane on the substrate has the same convex shape. 
     In the thin-film magnetic head of the present invention, the magnetic core which incorporates therein the front body of the magnetic pole and the rear body of the magnetic pole is formed as the first step by having a magnetic material embedded by collimation sputter by the use of a collimator of the shape of an orifice in a trench which is destined to serve as a site for the formation of the front body of the magnetic pole and the rear of the magnetic pole. As a result, the accuracy of positioning of the front body of the magnetic pole which has undergone the decrease of track width can be notably exalted and, at the same time, the magnetic core of the shape described above can be obtained in an ideal quality without entrapping any void therein. Further, the magnetic core can be formed in a state devoid of any difference of level. These features ensure impartation of a narrow track of high accuracy and very small tolerance, permit generation of a uniform magnetic flux density in the gap, and allow a head of uniform quality to be manufactured with high repeatability and great ease. 
     Further, in the thin-film magnetic head of this invention, in case that at least the front body of the magnetic pole is formed by having a magnetic material embedded by collimation sputter by the use of a collimator of the shape of an orifice in the trench formed in advance in part of the insulating layer, it is desirable to chamfer the upper outer edges of the lateral walls of the trench or the outer edges of the bottom surface of the trench. At that time, the trench is substantially provided with a taper of at least two steps. Thus, by the chamfering, the angle of the taper of the lateral walls near the bottom parts of the lateral walls or near the upper parts of the lateral walls is provided to be smaller than that of the remaining parts of the above parts of the lateral walls. As a result, the high-frequency permeability can be improved because the otherwise possible occurrence of a gross porosity during the embedment of the magnetic material by the collimation sputter can be completely prevented and because the magnetic anisotropy can be confined in the direction of track width. The trench which has the lateral walls having a taper of two or more steps can be easily produced by forming the insulating layer destined to contain the trench with two or more superposed films differing in etching grade and then etching the superposed films as by chemical etching or RIE. 
     Further, in this time, with respect to the upper magnetic core, the upper outer edges of the trench to form the front part of the magnetic pole is chamfered in such a manner that the taper angle near the bottom of the lateral walls is larger than the taper angle near the upper outer edges of the lateral walls. Further, with respect to the lower magnetic core, the outer edges of the bottom of the magnetic material in the front part of the magnetic pole is chamfered in such a manner that the taper angle near the upper outer edges of the lateral walls of the trench is larger than the taper angle of the lateral walls near the bottom of the trench. Thereby, the impartion of a track is accomplished with high accuracy. 
     Further, with respect to the front body of the magnetic pole of the upper magnetic core, when the taper angle near the bottom of the lateral walls of the trench is provided to be larger than the taper angle of the upper outer edges of the trench, the area of magnetic contact between the front body of the magnetic pole and the rear body of the magnetic pole can be enlarged and the magnetic path having small magnetic resistance can be formed. 
     A concrete thin-film magnetic head of the present invention is produced, for example, by the following steps of: 
     first, forming on a substrate sequentially a first insulating layer, an etching stopper layer, a second insulating layer, a polishing stopper layer, an etching mask, and a third insulating layer, forming a resist mask on the third insulating layer a portion for the formation of a trench for embedding therein a magnetic pole proper of a lower magnetic core, then forming the trench for embedding therein the magnetic pole proper by sequentially etching the third insulating layer, the etching mask, the polishing stopper layer, the second insulating layer, the etching stopper layer, and the first insulating layer, depositing a magnetic material by collimation sputter in the trench for embedding the lower magnetic pole proper, removing the excess magnetic material by polishing and/or etching back thereby enabling the portions of the third insulating layer, the etching mask, and the magnetic layer falling outside the trench to be flush with the polishing stopper layer, forming on the surface including the magnetic layer sequentially a magnetic gap layer, a fourth insulating layer, a second polishing stopper layer, and a fifth insulating layer, forming a second resist mask on a predetermined region, then removing by etching the fifth insulating layer, the second polishing stopper layer, and the fourth insulating layer thereby forming a trench for embedding a front body of a magnetic pole of a upper magnetic core and a trench for embedding a rear body of the magnetic pole of the lower magnetic core, depositing by collimation sputter a magnetic material in the trench for embedding the front body of the magnetic pole and the trench for embedding the rear body of the magnetic pole, removing by polishing or etching back the excess magnetic material thereby enabling the portions of the fifth insulating layer, the magnetic layer, and the second polishing stopper layer falling outside the trenches mentioned above to be flush with the second polishing stopper layer, forming the front body of the magnetic pole and the rear body of the magnetic pole, forming an insulating layer having a coil embedded in a plane including the front body of the magnetic pole, further forming a magnetic layer destined to serve as a rear body of the magnetic pole on part of the surface of the front body of the magnetic pole of the upper magnetic core and the insulating layer having the coil embedded therein, and forming a protective layer on the surface including the magnetic layer destined to serve as the rear body of the magnetic pole. 
     The fourth thin-film magnetic head of the present invention comprises a magnetic gap disposed to be positioned on an air bearing surface of the magnetic head, a pair of magnetic poles disposed to hold the magnetic gap therebetween, and a coil positioned between the pair of the magnetic poles to intersect the magnetic poles, wherein at least one of the magnetic poles being composed of a T-shaped magnetic pole, the T-shaped magnetic pole comprising a front part of a magnetic pole contacting with the magnetic gap, an intermediate part of a magnetic pole lying on the front part, and a rear part of a magnetic pole lying on the intermediate part. 
     And a width of the front part roughly defines a track width, the rear part has a wider width in a direction of track width than a width of the front part, and the intermediate part contacts with the rear part at an entire width of the rear part at the air bearing surface and has a narrower width at a contacting face with the front part than the width of the rear part. 
     The fifth thin-film magnetic head of the present invention comprises a pair of magnetic poles with a magnetic gap therebetween, and a coil interposed between the pair magnetic poles, wherein at least one of the magnetic poles comprises a front part of a magnetic pole, the front part being arranged in contact with the magnetic gap, and a rear part of the magnetic pole disposed on the front part, the rear part having a wider width in a direction of track width than a width of the front part, the rear part and a portion of the front part opposite to the magnetic gap being recessed from an air bearing surface of the magnetic pole. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially sectioned perspective view schematically illustrating the construction of a thin-film magnetic head obtained in Embodiment 1 of this invention. 
     FIG. 2 is a longitudinal cross section of the thin-film magnetic head of Embodiment 1 of this invention illustrated in FIG.  1 . 
     FIGS. 3A,  3 B, and  3 C are a series of longitudinal cross sections depicting part of a process for the manufacture of the thin-film magnetic head indicated in Embodiment 1 of this invention. 
     FIGS. 4A,  4 B,  4 C, and  4 D are a series of longitudinal cross sections depicting a process following the process for the manufacture of the thin-film magnetic head illustrated in FIG.  3 . 
     FIG. 5 is a longitudinal cross section of another thin-film magnetic head explained in comparison with the thin-film magnetic head of Embodiment 1 illustrated in FIG.  2 . 
     FIG. 6A is a detailed cross section of still another thin-film magnetic head explained in comparison with the thin-film magnetic head of Embodiment 1 illustrated in FIG.  2 . 
     FIG. 6B is an explanatory diagram of the flow of a magnetic flux in another thin-film magnetic head explained in comparison with the thin-film magnetic head of Embodiment 1 illustrated in FIG.  2 . 
     FIG. 7 is a longitudinal cross section illustrating the construction of a thin-film magnetic head obtained in Embodiment 2 of the present invention. 
     FIG. 8 is a longitudinal cross section illustrating the construction of a thin-film magnetic head obtained in Embodiment 3 of the present invention. 
     FIGS. 9A,  9 B, and  9 C are a series of longitudinal cross sections to aid in the explanation of a process for the production of the essential part of the thin-film magnetic head of Embodiment 3 of this invention. 
     FIG. 10 is a longitudinal cross section illustrating the construction of a thin-film magnetic head obtained in Embodiment 4 of the present invention. 
     FIG. 11 is a partially sectioned perspective view depicting the construction of a conventional thin-film magnetic head. 
     FIG. 12 is a longitudinal cross section of the conventional thin-film magnetic head illustrated in FIG.  11 . 
     FIG. 13 is a longitudinal cross section illustrating another example of the construction of the conventional thin-film magnetic head. 
     FIG. 14 is a partially sectioned perspective view schematically illustrating the construction of a thin-film magnetic head obtained in Embodiment 5 of the present invention. 
     FIG. 15 is a diagram to aid in the explanation of the axis of easy magnetization of the front body of a magnetic pole in the thin-film magnetic head of Embodiment 5 of this invention illustrated in FIG.  14 . 
     FIG. 16 is a diagram to aid in the explanation of the axis of easy magnetization of the front part of a magnetic pole in the conventional thin-film magnetic head. 
     FIG. 17 is a diagram to aid in the explanation of the direction of magnetization of the rear body of a magnetic pole. 
     FIG. 18 is a diagram to aid in the explanation of the direction of magnetization of the front body of a magnetic pole. 
     FIG. 19 is a diagram to aid in the explanation of the axis of easy magnetization of a front part of a magnetic pole of a magnetic core in the thin-film magnetic head of the present invention. 
     FIG. 20 is a diagram illustrating another example of the shape of a magnetic core in the thin-film magnetic head of Embodiment 5 of this invention illustrated in FIG.  14 . 
     FIGS. 21A,  21 B, and  21 C are a series of cross sections to aid in the explanation of a process for the production of the essential part of the thin-film magnetic head of Embodiment 5 of this invention. 
     FIGS. 22A,  22 B,  22 C, and  22 D are a series of cross sections to aid in the explanation of a process for the production of the essential part of the thin-film magnetic head of Embodiment 5 of this invention following the process of FIG.  18 . 
     FIG. 23 is a diagram to aid in the explanation of collimation sputter to be used in the process for the production of the thin-film magnetic head of this invention. 
     FIG. 24 is a diagram to aid in the explanation of ordinary collimation sputtering. 
     FIGS. 25A,  25 B, and  25 C are characteristic diagrams illustrating results of the determination of a MH loop in the front part of a magnetic pole of an lower magnetic core in the thin-film magnetic head of Embodiment 5 of the present invention. 
     FIG. 26 is a characteristic diagram illustrating a result of the determination of a MH loop in the front part of a magnetic pole of an upper magnetic core in the thin-film magnetic head material of Embodiment 5 of the present invention. 
     FIGS. 27A,  27 B, and  27 C are a series of longitudinal cross sections to aid in the explanation of a process for the production of the essential part of a thin-film magnetic head obtained in Embodiment 6 of the present invention. 
     FIG. 28 is an explanatory diagram illustrating with a model the manner in which a trench formed with lateral walls of an ordinary one-step taper is filled with a magnetic material. 
     FIG. 29 is an explanatory diagram illustrating with a model the manner in which a trench formed with lateral walls containing a two-step taper is filled with a magnetic material as described in Embodiment 6 of the present invention. 
     FIG. 30 is an explanatory diagram illustrating with a model the manner in which a trench formed with lateral walls containing a three-step taper is filled with a magnetic material as described in Embodiment 6 of the present invention. 
     FIGS. 31A,  31 B,  31 C,  31 D, and  31 E are a series of longitudinal cross sections to aid in the explanation of a process for the production of the essential part of a thin-film magnetic head obtained in Embodiment 7 of the present invention. 
     FIGS. 32A and 32B are a series of explanatory diagrams illustrating with a model the manner in which a trench formed with lateral walls containing a two-step taper is filled with a magnetic material as described in Embodiment 7 of the present invention. 
     FIG. 33 is a graph showing the taper angle dependency of the specific permeability of a stripe as described in Embodiment 7 of the present invention. 
     FIG. 34 is a graph showing the taper angle dependency of the head efficiency as described in Embodiment 7 of the present invention. 
     FIG. 35 is a partially sectioned perspective view schematically illustrating the construction of an essential part of a thin-film magnetic head of Embodiment 8 which is applied to a recording-reproducing separate type magnetic head using a magnetoresistance effect element. 
     FIG. 36 is a perspective view illustrating an example of a magnetic pole structure in the neighborhood of an air bearing surface of the thin film magnetic head of the Embodiment 8. 
     FIG. 37 is a cross section of the magnetic pole structure of FIG. 36 depicted from an air bearing surface side. 
     FIG. 38 is a diagram of another example of a magnetic pole structure in the neighborhood of an air bearing surface of the thin film magnetic head of the Embodiment 8. 
     FIG. 39 is a diagram of another example of a magnetic pole structure in the neighborhood of an air bearing surface of the thin film magnetic head of the Embodiment 8. 
     FIG. 40 is a perspective view illustrating an example of a magnetic pole structure in the neighborhood of an air bearing surface of the thin film magnetic head of Embodiment 9, 
     FIG. 41 is a cross section of the magnetic pole structure of FIG. 40 depicted from an air bearing surface side. 
     FIG. 42 is a perspective view illustrating an example of a magnetic pole structure in the neighborhood of an air bearing surface of the thin film magnetic head of the Embodiment 10, 
     FIG. 43 is a cross section of the magnetic pole structure of Embodiment 11 depicted from an air bearing surface side. 
     FIG. 44 is a diagram for explaining a T-shaped magnetic pole structure of the present invention. 
     FIG. 45A is a diagram illustrating a cross section of a magnetic pole structure of Embodiment 12. 
     FIG.  45 A′ is a diagram illustrating a cross section of another magnetic pole structure of Embodiment 12. 
     FIG. 45B is a diagram illustrating a cross section of further other magnetic pole structure of Embodiment 12. 
     FIGS. 45C and 45D are diagrams for explaining the manufacturing process of the magnetic pole structure of FIG.  45 B. 
     FIG. 45E is a diagram illustrating a cross section of further other magnetic pole structure of Embodiment 12. 
     FIG. 45F is a diagram illustrating a cross section of further other magnetic pole structure of Embodiment 12. 
     FIG. 45G is a diagram illustrating a cross section of further other magnetic pole structure of Embodiment 12. 
     FIGS.  45 G′ and  45 G″ are diagrams for explaining the manufacturing process of the magnetic pole structure of FIG.  45 G. 
     FIG. 45H is a diagram illustrating a cross section of further other magnetic pole structure of Embodiment 12. 
     FIG. 46 is a perspective view illustrating an example of a magnetic pole structure in the neighborhood of an air bearing surface of a conventional thin-film magnetic head. 
     FIG. 47 is a perspective view illustrating an example of a T-shaped magnetic pole structure in the neighborhood of an air bearing surface of a thin film magnetic head. 
     FIG. 48 is a diagram illustrating an Off-track profile recorded by the thin-film magnetic head having a T-shaped magnetic pole. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, the embodiments of this invention will be described below with reference to the annexed drawings. 
     Embodiment 1 
     FIG.  1  and FIG. 2 are diagrams illustrating the construction of the essential part of a thin-film magnetic head according to Embodiment 1 of this Invention; FIG. 1 being a partially sectioned perspective view schematically illustrating the construction of the thin-film magnetic head and FIG. 2 a longitudinal cross section thereof. 
     In these diagrams,  11  stands for a substrate which is made of Al 2 O 3 ·TiC. On this substrate  11 , a magnetic pole proper  14   a  of a lower magnetic core  14  formed with a laminated magnetic material of CoZrNb is superposed through the medium of an insulating layer  12  made of Al 2 O 3  and an etching stopper layer  13 . On the magnetic pole proper  14   a , a magnetic gap  15  made of Al 2 O 3  and concurrently serving as an etching stopper layer is formed. 
     On this magnetic gap  15  on the side of the surface thereof opposite a medium, a front body  16   a  of a magnetic pole of an upper magnetic core  16  formed with a laminated magnetic material of CoZrNb is superposed. The front body  16   a  of the magnetic pole has substantially the shape of a rectangular solid. At the back of the front body  16   a  of the magnetic pole, a rear auxiliary body  14   b  of the lower magnetic core  14  which is magnetically isolated by an insulating layer  17  is formed. On the layers mentioned above, a coil  19  make of Cu and embedded in an insulating layer  18  made of polyimide is formed. 
     On the insulating layer  18 , a rear body  16   b  of a magnetic pole of the upper magnetic core  16  held in partly surface contact in a plane with the front body  16   a  of the upper magnetic pole is disposed in a laminated structure. Then, a protective layer  20  made of Al 2 O 3  is superposed on the front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole to complete the formation of the essential part of an electromagnetic transducer of the thin-film magnetic head. 
     The magnetic pole proper  14   a  of the lower magnetic core  14  and the rear auxiliary body  14   b  of the magnetic pole and the front body  16   a  of the magnetic pole of the upper magnetic core  16  and the rear body  16   b  of the magnetic pole as well are invariably in such a construction as to have laminated magnetic layers  22  of CoZrNb joined to each other through the medium of a nonmagnetic layer  21  made of Al 2 O 3 . An insulating layer  23  made of SiO 2  is disposed around the magnetic pole proper  14   a  so as to fix the position for the formation thereof. At the back of the rear auxiliary body  14   b , a coil drawer line  24  is disposed, Further, polishing stopper layers  25  are disposed one each on the insulating layer  17  and  23 . 
     Now, the process for producing the thin-film magnetic head constructed as described above will be explained below with reference to FIG.  3  and FIG.  4 . 
     First, the insulating layer  12  having a thickness of about 5 μm and made of Al 2 O 3 , the etching stopper layer  13  having a thickness of about 0.1 μm, the insulating layer  23  having a thickness of about 3 μm and made of SiO 2 , the polishing stopper layer  25  having a thickness of about 0.1 μm and made of Al 2 O 3 , an etching mask  26  having a thickness of about 0.2 μm, and an insulating layer  27  having a thickness of about 0.5 μm and made of SiO 2  are superposed on the substrate  11  as shown in FIG.  3 A. The insulating layer  27  in this case is destined to discharge the part of stock for cutting at the subsequent step of polishing. 
     The etching stopper layer  13  and the etching mask  26  mentioned above are desired to be made of a material which is etched slowly by a fluorine type reactive gas. Concrete examples of the material of this description include Al 2 O 3 , C, Al, Ti, Cr, W, Nb, and Si. The polishing stopper layer  25  is desired to be made of such a material as Al 2 O 3  which is not easily removed by polishing. 
     After a resist mask (not shown) is subsequently superposed on the flat smooth insulating layer  27 , the insulating layer  27  is etched with such an etching gas as CF 4 , then the etching mask  26  with such a gas as O 2 , subsequently the polishing stopper layer  25  with a gas prepared by adding argon as to CF 4 , and finally the insulating layer  23  with such a gas as CF 4  by means of RIE (reactive ion etching). Thereafter, the resist mask is removed to obtain a trench  28  for embedding the magnetic pole proper  14   a  as shown in FIG.  3 B. 
     In this case, since the etching mask  26  is already formed as described above, the lateral walls to define the trench  28  may be cut perpendicularly or may be converged or diverged in the direction of depth. Further, owing to the presence of the etching stopper layer  13 , the depth of the embedding trench  28  can be accurately controlled and the shapes of the bottom edges of this trench  28  can be controlled as well by dint of suitable excessive etching. The bottom edges of the trench  28  may be curved with a suitable radius or may be cut substantially rectangularly, for example. 
     Then, inside the trench  28 , the materials which go to form a laminated magnetic material for the magnetic pole proper  14   a , namely the magnetic layer  22  made of CoZrNb and the nonmagnetic layer  21  made of Al 2 O 3  are sequentially deposited as by collimation sputter as shown in FIG.  3 C. Subsequently, the extraneous remnant, if any, from the deposition are removed from the trench  28  as by polishing or etching back to complete the formation of the magnetic pole proper  14   a.    
     When the bottom edges of the trench  28  were smoothly curved with a radius at the preceding step, the magnetic characteristics in the edge parts of the magnetic layer  14   a  to be embedded can be easily controlled at the current step. The two polishing stopper layers  25  made of such a material as Al 2 O 3  which is not easily removed by polishing are disposed each on the opposite sides of the upper surface of the magnetic pole proper  14   a . If the polishing work proceeds in a more or less inclined direction during the step of polishing, therefore, the polishing stopper layers  25  will function as a stopper and serve the purpose of correcting the inclination and consequently permit control of the thickness of the magnetic pole proper  14   a.    
     Then, the magnetic gap  15  having a thickness of about 0.1 μm, the insulating layer  17  having a thickness of about 3 μm, the polishing stopper layer  25  having a thickness of about 0.1 μm, and the insulating layer  27  intended as stock for cutting and having a thickness of about 0.5 μm are sequentially superposed on the magnetic pole proper  14   a  as shown in FIG.  4 A. The materials to be used for the layers herein are the same as those of the layers involved in the process shown in FIG.  3 A. After the resist mask is subsequently formed, the insulating layer  27  as the stock for cutting, the polishing stopper layer  25 , and the insulating layer  17  are etched in the same manner as in the process described above. In consequence of this etching operation, a trench  29   a  for embedding the front body  16   a  of the magnetic pole and a trench  29   b  for embedding the rear auxiliary body  14   b  of the magnetic pole are obtained as shown in FIG.  4 B. In the formation of these trenches  29 , the lateral walls to define the trenches can be formed in a desired shape in the same manner as in the process described above. 
     The magnetic gap  15  is intended to serve concurrently as an etching stopper layer during the etching operation mentioned above and, therefore, is desired to be made of such a material as Al 2 O 3 , for example, which is etched slowly by a fluorine type reactive gas and is capable of functioning as a magnetic gap. The fact that the magnetic gap  15  concurrently fulfills the part of an etching stopper layer as described above contributes to exalt the yield because the gap retains its size intact even when the etching work involved in the formation of the trench for the front body  16   a  of the magnetic pole is carried out more or less excessively. In this case, it is optional with the manufacturer to overlay the gap preparatorily with an etching stopper made of C, then forming the trench, and thereafter removing the etching stopper of C as by means of an O 2  plasma thereby exposing the gap. 
     Then, the materials for forming a two-layer laminated magnetic layers ( 22 / 21 / 22 ) are deposited by the collimation sputter inside each of the trenches  29   a ,  29   b  as shown in FIG. 4C, then the extraneous remnant, if any, from the sputtering is removed by polishing or etching back, and the front body  16   a  of the magnetic pole and the rear auxiliary body  14   b  of the magnetic pole both having Substantially the shape of a rectangular solid are formed by embedding. In the present embodiment, the coil drawer line  24  is simultaneously formed by embedding. The fact that the front body  16   a  of the magnetic pole, the rear auxiliary body  14   b  of the magnetic pole, and further the coil drawer line  24  are formed simultaneously by embedding permits a generous cut in the number of man-hours to be involved. 
     Then, the insulating layer  18  made of polyimide resin and having embedded therein the coil  19  made of Cu is superposed on the front body  16   a  of the magnetic pole and the rear auxiliary body  14   b  of the magnetic pole. The two-layer laminated magnetic material destined to serve as the rear body  16   b  of the magnetic pole and the protective layer  20  made of Al 2 O 3  are further superposed thereon to complete the formation of the electromagnetic transducer of the thin-film magnetic head of this invention. In the process described above, the magnetic gap  15  may be formed as by means of the collimation sputter before the laminated magnetic material destined to form the front body  16   a  of the magnetic pole and the rear auxiliary body  14   b  of the magnetic pole is shaped by the collimation sputter. 
     In accordance with the construction and the method for production of the thin-film magnetic head of the embodiment described above, a narrow track having a width of not more than I μm can be imparted to the head at a tolerance ( 3 σ) within ±0.1 μm with high accuracy and high repeatability because the front body  16   a  of the magnetic pole having substantially the shape of a rectangular solid is formed by embedding the component materials for the laminated magnetic material inside the trench  29   a  formed of the insulating layer  17 . Specifically, the positional accuracy of the front body  16   a  of the magnetic pole can be markedly improved because the trench  29   a  destined to serve as the site for the formation of the front body  16   a  is shaped in a state devoid of difference of level. Then, since the front body  16   a  of the magnetic pole having substantially the shape of a rectangular solid is formed by embedding the magnetic material by means of the collimation sputter inside the trench  29   a , it can be obtained in high quality without entrapping any void therein in a highly accurately positioned state. 
     The front part of the magnetic pole is enabled to tolerate a heat treatment at elevated temperatures up to about 500° C. because it is wholly formed of an inorganic material excelling in resistance to heat, and at the same time, it is completely formed before the insulating layer  18  and the like in which the coil  19  is to be embedded are formed. As a result, the uniaxial anisotropy having only small dispersion of anisotropy can be imparted to the magnetic material having a high saturation flux density. Further, in the thin-film magnetic head mentioned above, the thickness of the magnetic layer  22  can be descreased and the axis of easy magnetization can be parallelized with the track width even when the track is formed in a decreased width because the two-layer laminated magnetic material incorporating therein the nonmagnetic layer  21  made of Al 2 O 3  is used for the lower magnetic core  14  and the upper magnetic core  16 . This laminated magnetic material fully manifests the expected effect so long as the number of component layers which form the laminate is at least three. 
     Besides, in the thin-film magnetic head of the present embodiment, the initial part of taper of the insulating layer  18  having the coil  19  embedded therein is set behind the rear end part of the front body  16   a  of the magnetic pole and the rear body part  16   b  of the magnetic pole is held in surface contact in a plane with the rear end part of the front body  16   a  of the magnetic pole and is bent on the backward side from the rear end part of the front body  16   a  of the magnetic pole. Owing to this very arrangement, the head can be obtained in uniform quality with high efficiency because the front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole are allowed to retain their surface contact intact even when the point of bend is more or less deviated. Further, the thorough surface contact serves the purpose of precluding the otherwise possible occurrence of noise as of wiggle. These features allow a polyimide type organic insulating material having no very satisfactory patterning accuracy to be used in the place of a resist material for the insulating layer  18  and permit adoption of a magnetic material having a high saturation flux density and consequently necessitating an annealing treatment in the neighborhood of 350° C. 
     If the initial part of taper of the insulating layer  19  is set nearer to the surface opposite the medium than to the rear end part of the front body  16   a  of the magnetic pole as shown in FIG. 5, for example, the area of contact between the front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole is decreased possibly to the extent of not merely degrading the efficiency but also inducing misalignment capable of greatly aggravating the degradation of efficiency and further breaking the uniformity of product quality. 
     Further, in the thin-film magnetic head of the present embodiment, the possible occurrence at the surface opposite the medium to the medium of leakage of magnetic flux near the point of contact between the front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole in which the magnetic material assumes an incontinuously bent form can be prevented because the front end part of the rear body  16   b  of the magnetic pole is disposed as recessed from the surface opposite the medium (indicated by A in the diagram). As a result, the adverse effects of the leakage of magnetic flux at the surface opposite the medium on the operations of recording and regeneration can be eliminated. If the end part of the rear body  16   b  of the magnetic pole is extended to the surface opposite the medium as shown in FIG. 6A, for example, the leakage of magnetic flux at the surface opposite the medium (indicated by B in the diagram) occurs conspicuously as shown in FIG. 6B, with the possible result that the recording will be attained not merely between tracks but also across adjacent tracks. Further, during the course of the regeneration, the leakage goes to aggravate the stroke noise. On the other hand, these adverse effects can be eliminated by causing the rear body  16   b  of the magnetic pole to be recessed from the surface opposite the medium. 
     In the construction of the present invention described above, if the surface of contact between the rear body  16   b  of the magnetic pole and the front body  16   a  of the magnetic pole is not a perfect plane as when this surface of contact contains rises and falls, the magnetic flux is swelled across this surface of contact and is no longer allowed to flow easily. Thus, the magnetic flux of required quality is obtained only with difficulty. 
     The embodiment described above represents a case of embedding the magnetic material by sputtering in the trench of SiO 2  formed by means of RIE. It is optional with the manufacturer to adopt instead a conventional procedures which comprises first forming a film of the magnetic material, then shaping the magnetic material by means of ion milling or RIE, and subsequently overlaying the shaped magnetic material with the Insulating layer and polishing back the coated magnetic material. This procedure, however, impairs the accuracy of track width, though to a slight extent. 
     Embodiment 2 
     Now, another embodiment of this invention will be described below with reference to FIG.  7 . 
     FIG. 7 illustrates a thin-film magnetic film which has a lower magnetic core  31  composed of a front body  31   a  of a magnetic pole having substantially the shape of a rectangular solid and a rear body  31   b  of the magnetic pole held in surface contact in a plane with the front body  31   a  of the magnetic pole. Specifically, the front body  31   a  of the magnetic pole of the lower magnetic core and the insulating layer  18  having the coil  19  embedded therein are formed as embedded in the insulating layer  12 . On these layers, a rear auxiliary body  32   b  of an upper magnetic core  32  magnetically isolated by the insulating layer  17  from the front body  31   a  of the magnetic pole of the lower magnetic coil and the coil drawer line  24  are superposed so as to be flush with each other. A magnetic pole proper  32   a  of the upper magnetic core  32  is superposed further thereon through the medium of the magnetic gap  15 . The protective layer  20  is superposed on the upper magnetic pole proper  32   a  to complete the formation of the essential part of the electromagnetic transducer of the thin-film magnetic head. 
     In the thin-film magnetic head of the present embodiment, .similarly to the embodiment described previously, the front body  31   a  of the magnetic pole having substantially the shape of a rectangular solid is manufactured by forming a trench for embedding the front body  31   a  of the magnetic pole with the insulating layer  17 , embedding a magnetic material by collimation sputter inside the trench, and then removing the extraneous remnant, if any, from the sputtering as by polishing. Though FIG. 7 omits such component layers as the polishing stopper layer and the etching stopper layer from illustration, they may be formed as occasion demands similarly to the embodiment described previously. While the magnetic cores are depicted as severally formed with a single layer for the sake of simplicity of illustration, they may be formed of a laminated magnetic material in the same matter as in the embodiment described previously. This remark holds good for the following embodiments. 
     In the thin-film magnetic head of the embodiment described above, since the front body  31   a  of the magnetic pole having substantially the shape of a rectangular solid is manufactured by causing the magnetic material to be embedded by means of the collimation sputter within the trench formed as of the insulating layer  17 , the relevant parts can be shaped in a state devoid of any difference of level. Thus, the head enables a narrow track of extremely small tolerance to be imparted thereto with high accuracy and repeatability. The other effects of the head are likewise satisfactory. Further, in terms of the process of manufacture, the present embodiment permits a generous cut in the number of man-hours to be involved because the front body  31   a  of the magnetic pole, the rear auxiliary body  32   b  of the magnetic pole, and the coil drawer line  24  are simultaneously formed by one and the same embedding operation. 
     Embodiment 3 
     FIG. 8 illustrates a thin-film magnetic head having a lower magnetic core  33  and an upper magnetic core  34  respectively composed of front bodies  33   a ,  34   a  of a magnetic pole having substantially the shape of a rectangular solid and rear bodies  33   b  and  34   b  of the magnetic pole held in surface contact in a plane with the front bodies  33   a ,  34   a  of the magnetic pole. Specifically, on the insulating layer  12  is superposed the rear body  33   b  of the magnetic pole of the lower magnetic coil. The front body  33   a  of the magnetic pole of the lower magnetic coil and a rear auxiliary body  33   c  of the magnetic pole of the lower magnetic coil are superposed further thereon. The front body  34   a  of the magnetic pole of the upper magnetic core and a rear auxiliary body  34   c  of the magnetic pole of the lower magnetic coil and the coil drawer line  24  are superposed through the medium of the magnetic gap  15  on the front body  33   a  of the magnetic pole of the lower magnetic coil and the rear auxiliary body  33   c  of the magnetic pole of the lower magnetic coil. Then, in the same manner as in the first embodiment, the insulating layer  18  having the coil  19  embedded therein, the rear body  34   b  of the magnetic pole of the upper magnetic coil so formed as to overlie the insulating layer  18 , and the protective layer  20  are further superposed to complete the formation of the essential part of the electromagnetic transducer of the thin-film magnetic head. 
     The thin-film magnetic head having the construction described above is manufactured, for example, as follows. An insulating layer  35  is superposed on the rear body  33   b  of the magnetic pole formed on the insulating layer  12  and a trench  36  is incised in the insulating layer  35  as by means of RIE as shown in FIG.  9 A. During the incision of the trench, the walls defining the trench are either perpendicularly cut or slightly diverged in the direction of depth and are suitably etched excessively to provide the trench  36  with substantially rectangular bottom edges. 
     Then, with the collimator so adjusted as to eject supper particles in a direction substantially parallel with the lateral walls of the trench  36 , the magnetic material to form the lower magnetic core  33 , the material to form the magnetic gap  15 , and the magnetic material to form the upper magnetic core  34  are continuously sputtered by the collimator into the same trench  36 . Then, by polishing back the resultant product of sputtering, the front bodies  33   a ,  34   a  and the rear auxiliary bodies  33   c ,  34   c  respectively of the magnetic poles are formed as shown in FIG.  9 C. 
     By constructing the lower magnetic core  33  and the upper magnetic core  34  so as to be provided respectively with the front bodies  33   a  and  34   a  of the magnetic pole, and at the same time, continuously manufacturing the upper and lower front bodies  33   a  and  34   a  of the magnetic pole in one and the same embedding process as described above, the otherwise possible misalignment of the upper and lower front bodies  33   a  and  34   a  of the magnetic pole can be perfectly prevented. As a result, the upper and the lower pole in the produced head have identical widths and are perfectly aligned with each other. As a natural consequence, the burden of side righting by means of side fringing can be minimized and the track pitch can be decreased. 
     As respects the process of manufacture involved in the embodiment described above, the number of man-hours required fox the manufacture can be notably cut because the upper and lower front bodies  33   a  and  34   a  of the magnetic pole, the rear auxiliary bodies  33   c  and  34   c  of the magnetic poles, the magnetic gap  15 , and the coll, drawer line  24  are simultaneously manufactured in one and the same embedding process. 
     Embodiment 4 
     FIG. 10 illustrates a case of simultaneously manufacturing the coil  19  and the front body  16   a  of the magnetic pole of the upper magnetic coil with one and the same material in one and the same embedding process and simultaneously manufacturing the coil drawer line  24  and the lower magnetic core  14  with one and the same material in one and the same embedding process. This procedure permits a marked cut in the number of man-hours involved in the operation. The head produced in this case satisfactorily fulfills its function so long as it is used exclusively for recording. When pure iron is used as the material under discussion, the specific resistance can be confined to 15 μ□·cm. It is optional with the manufacturer to produce the coil and the front body of the magnetic pole of the lower magnetic coil with one and the same material in one and the same embedding process. 
     Embodiment 5 
     FIG. 14 is a partially sectioned perspective view schematically illustrating the construction of the essential part of a thin-film magnetic head according to Embodiment 5 of the present invention. 
     In this diagram,  11  stands for a substrate which is made as of Al 2 O 3 ·Tic. On this substrate  11 , a magnetic pole proper  14   a  of a lower magnetic core  14  made of such a magnetic material as CoZrNb, for example, is superposed through the medium of an insulating layer  12  made of Al 2 O 3  and an etching stopper layer  13 . The magnetic pole proper  14   a  which has a substantially convex shape is composed of a front part of the magnetic pole proper having substantially the shape of a rectangular solid corresponding to the convex projecting part and a rear part of the magnetic pole proper. The front part of the magnetic pole proper and the rear part of the magnetic pole proper are formed continuously on one and the same plane. On the magnetic pole proper  14   a  is superposed a magnetic gap  15  which is made of Al 2 O 3 and intended to serve concurrently as an etching stopper layer. 
     On the magnetic gap  15  on the side of the surface thereof opposite the medium, a front body  16   a  of an magnetic pole of an upper magnetic core  16  made of such a magnetic material as CoZrNb is superposed. The front body  16   a  of the magnetic pole has substantially the shape of a rectangular solid. Behind the back of the front body  16   a  of the magnetic pole, the rear auxiliary body  14   b  of the magnetic pole of a lower magnetic coil  14  magnetically isolated by an insulating layer  17  is formed. On these layers, a coil  19  made of Cu and embedded in an insulating layer  18  made of polyimide is superposed. 
     On the insulating layer  18 , a rear body  16   b  of the magnetic pole of the upper magnetic core  16  held in surface contact in a plane with the front body  16   a  of the upper magnetic pole is superposed. The front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole, as viewed in a planar aspect, are so shaped that, similarly to the magnetic pole proper  14   a  mentioned above, the rear body  16   b  of the magnetic pole is connected at an angle in the range of from 90 to 120 degrees to the front body  16   a  of the magnetic pole which corresponds to a convex projection. In other words, they form a generally convex projection on the substrate  11 . Then, the front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole are overlaid with a protective layer made of Al 2 O 3  and omitted from illustration to complete the formation of the essential part of an electromagnetic transducer of the thin-film magnetic head. 
     An insulating layer  23  made of SiO 2  and intended to define the position of formation of the magnetic pole proper  14   a  is disposed around the magnetic pole proper  14   a . A coil drawer line  24  made of the same material as the magnetic material is provided behind the back of the rear auxiliary body  14   b  of the magnetic pole. 
     The angle θ of connection between the magnetic pole proper  14   a  in the lower magnetic core  14  and the front part of the magnetic pole in the upper magnetic core  16  and a rear part of the magnetic pole is restricted to within the range of from 90 to 120 degrees so that the axis of easy magnetization of the front part of the magnetic pole will be stably parallelized with the direction of track width even when the track is formed in a decreased width. If the angle θ of connection exceeds 120 degrees, the axis of easy magnetization will tend to be oriented in a direction perpendicular to the direction of track width as shown in FIG.  16 . This appears particularly when the track width is decreased below 3 μm. Preferably, the angle θ of connection mentioned above is restricted to within the range of from 90 to 100 degrees. For the sake of converging the magnetic fluxes of the rear part of the magnetic pole in the front part of the magnetic pole, however, the magnitude of the angle θ of connection is desired to be increased to a certain extent. Thus, it is desirable to set the angle θ of connection with due respect to the impartation of the axis of easy magnetization mentioned above and the convergence of the magnetic fluxes. For the sake of the convergence of the magnetic fluxes, the opposite end parts C and C of the rear part of the magnetic pole which is connected to the front part of the magnetic pole are desired to be curved as shown in FIG. 20, for example. By this measure, the angle θ of connection can be approximated to 90 degrees, and at the same time, the convergence of magnetic fluxes can be promoted. 
     Now, the process by which the thin-film magnetic head constructed as described above is manufactured will be explained below with reference to FIGS. 21A,  21 B, and  21 C and FIGS. 22A,  22 B,  22 C, and  22 D. 
     First, the insulating layer  12  having a thickness of about 5 μm and made of Al 2 O 3 , the etching stopper layer  13  having a thickness of about 0.1 μm, and the insulating layer  23  having a thickness of about 3.5 μm and made of SiO 2  are sequentially superposed on the substrate  11  as shown in FIG.  21 A. The insulating layer  23  is to be formed in such a thickness as to include stock for cutting which is necessary in the subsequent polishing process. It is optional with the manufacturer to form the insulating layer  23  in the stated thickness in advance and then overlay an extra SiO 2  layer fated to serve as the stock for cutting on the insulating layer  23  through the medium such as of a polishing stopper layer and an etching mask. 
     Then, the insulating layer  23  which is flat and smooth is overlaid with a resist mask (not shown) and etched with such an etching gas as CF 4  to form a trench  28  of an approximately convex shape corresponding to the part for forming the lower magnetic pole proper  14   a  as shown in FIG.  18 B. 
     Now, a magnetic material destined to form the magnetic pole proper  14   a  is deposited inside the trench  28  by means of the collimation sputter with a collimator of the shape of an orifice and the extraneous remnant, if any, from the sputtering is removed as by polishing to complete the formation of the lower magnetic pole proper  14   a  which is composed of the convex shaped front part of the magnetic pole and the rear part of the magnetic pole. 
     Here, the collimation sputter of the magnetic material for the formation of the magnetic pole proper  14   a  is desired to carry out by the use of an orificial collimator  41  as shown in FIG.  23 . This orificial collimator  41  serves the purpose of repressing flight of sputter particles in the direction of width thereof. The use of this orificial collimator  41  permits the rate of sputtering to be increased to at least three times the rate which is obtained when such an ordinary collimator  42  as shown in FIG. 24, for example, is used. In the diagram,  43  stands for a sputter target and  44  for a substrate to be overlaid. 
     The orificial collimator  41  described above is desired to be so disposed that the longitudinal direction thereof will fall substantially perpendicularly to the direction of track width of the magnetic core (indicated by the arrow Z in the diagram). Then, the minute portion of the trench  28  which corresponds to the part for the formation of the front part of the magnetic pole can be ideally filled with the sputter particles without entrapping a void therein because the direction in which the front part of the magnetic pole is projected coincides with the direction of flight of the sputter particles. This embedment of the magnetic material in the front part of the magnetic pole is affected also by the shape of the magnetic pole proper  14   a . If the rear part of the magnetic pole is connected at an angle exceeding  120  degrees, a magnitude fit for a fan, relative to the front part of the magnetic pole as shown in FIG. 16, voids (cavities) tend to occur specifically in the basal portion of the front part of the magnetic pole in spite of the use of the orificial collimator  41  described above because the sputter particles are suffered to disperse in the directions perpendicular to the sides of the fan. The occurrence of voids particularly in the front part of the magnetic pole can be precluded by constructing the magnetic pole proper  14   a  so that the rear part of the magnetic pole may be connected at an angle in the range of from 90 to 120 degrees to the part of the magnetic pole. The ease with which such voids as are entrapped in the magnetic core of the conventional shape tend to occur mounts in accordance as the angle formed between the longitudinal direction of the orificialy collimator  41  and the direction of track width deviates from the approximate right angle. Thus, the orificial collimator  41  is desired to be so disposed that the longitudinal direction thereof will fall substantially perpendicularly to the direction of track width. 
     Then, the magnetic gap  15  having a thickness of about 0.1 μm and the insulating layer  17  having a thickness of about 3.5 μm are sequentially superposed on the magnetic pole proper  14   a  as shown in FIG.  22 A. Incidentally, this insulating layer  17  is to be formed in a thickness including stock for cutting which is required at the subsequent polishing process. It is optional with the manufacturer to overlay the insulating layer  17  with a polishing stopper layer, an etching mask, and a SiO 2  layer fated to serve as the stock for cutting similarly to the process shown in FIG.  21 A. Then, the insulating layer  17  is overlaid with a resist mask and then etched similarly to the process described above. In consequence of this etching, a trench  29   a  for embedding the front body  16   a  of the magnetic pole and a trench  29   b  for embedding the rear auxiliary body  14   b  of the lower magnetic pole will be obtained as shown in FIG.  22 B. 
     Here, the magnetic gap  15  is intended to serve concurrently as an etching stopper layer during the course of the etching operation mentioned above. It is, therefore, desired to be formed of such a material as Al 2 O 3 , for example, which is etched slowly with a fluorine type reactive gas and is allowed to fulfil the function of a magnetic gap. The fact that the magnetic gap  15  concurrently discharges the part of an etching stopper layer as described above contributes to promote the exaltation of the yield because the gap is enabled to retain its size intact even when the etching performed for the formation of the trench in the front body  16   a  of the magnetic pole is carried out more or less excessively. 
     Now, a magnetic material is deposited by means of the collimation sputter by the use of an orificial collimator inside the trenches  29   a  and  29   b  similarly to the embedding operation performed on the magnetic pole proper  14   a  as described above and then the extraneous remnant, if any, form the sputtering is removed as by polishing to form the front body  16   a  of the magnetic pole and the rear auxiliary body  14   b  of the magnetic pole both in the substantial shape of a rectangular solid as shown in FIG.  22 C. In the present embodiment, the coil drawer line  24  is simultaneously formed in the course of the embedding operation. 
     The insulating layer  18  made of polyimide resin and having embedded therein the coil  19  made of Cu is superposed on the front body  16   a  of the magnetic pole and the rear auxiliary body  14   b  of the magnetic pole and then the magnetic member destined to serve as the rear body  16   b  of the upper magnetic pole and a protective layer  20  made of Al 2 O 3  are further superposed thereon, to complete the formation of the electromagnetic transducer of the thin-film magnetic head of the present invention. During the process described above, it is optional with the manufacturer to form the magnetic gap  15  by means of the collimation sputter before the magnetic materials destined to form the front body  16   a  of the magnetic pole and the rear auxiliary body  14   b  of the magnetic pole are formed by means of the collimation sputter. 
     In accordance with the construction of the thin-film magnetic head of the embodiment described above and the method for the manufacture thereof, the lower magnetic core  14  and the upper magnetic core  16  of a narrow track having the axis of easy magnetization of the front part of the magnetic pole parallelized with the direction of track width can be obtained stably and efficiently while satisfying the requirement as to the adaptability for mass production. FIG. 25 shows test results of the MH loop which the lower magnetic core  14  and the upper magnetic core  16  describe when the angle θ of contact between the front part of the magnetic pole and the rear part of the magnetic pole is varied. The test results shown in FIG. 25 are derived from an experiment using a track width fixed at 2 μm and applying a magnetic field in the direction of depth (the direction of excitation of the front part of the magnetic pole). FIGS. 25A,  25 B, and  25 C are characteristic diagrams showing the test results of the lower magnetic core  14 . It is clearly noted form FIGS. 25A and 25B that the axis of easy magnetization of the front part of the magnetic pole fall parallelly with the direction of track width when the angle θ of connection is in the range of from 90 to 120 degrees. In contrast thereto, as shown in FIG. 25C, the axis of easy magnetization falls perpendicularly to the direction of track width when the angle θ of connection exceeds 120 degrees. 
     FIG. 26 is a characteristic diagram showing the text results of the upper magnetic core  16 . The MH loop of the upper magnetic core shows substantially similar results as those of the lower magnetic core when the angle θ of connection is 90 or 135 degrees. In contrast thereto, it is noted from  26  that a complete linearity thereof can be obtained with a distinct difference from the lower magnetic core. From these results, it was confirmed that the partial superposition of the front part of the magnetic pole with the rear part of magnetic pole is effective to fall the axis of easy magnetization in the front part of the magnetic pole parallelly with the direction of track. 
     Further, in the lower magnetic core, the magnetic core composed of a laminate construction having a nonmagnetic layer of Al 2 O 3  interposed between two magnetic layers made of CoZrNb, with the angle of connection set at 120 degrees shows the same results as that shown in FIG.  26 . It was confirmed form FIG. 26 that the anisotropy of the axis of easy magnetization is further enhanced by forming the magnetic core with a laminated magnetic material. 
     Namely when the track width is decreased, the thickness of the magnetic layer can be decreased and the axis of easy magnetization can be easily parallelized with the direction of track width by using for the magnetic core the two-layer laminated magnetic material incorporating therein the nonmagnetic layer of Al 2 O 3  as described above. 
     In the embodiment described above, the front part of the magnetic pole which has the track width decreased to below 1 μm can be obtained with high accuracy and satisfactory repeatability and with a tolerance confined within ±0.1 μm because the magnetic pole proper  14   a  of the lower magnetic core  14  and the front body  16   a  of the magnetic pole of the upper magnetic core  16  are formed by in advance embedding a magnetic material by means of the collimation sputter within the trenches  28  and  29   a  formed as with the insulating layers  23  and  17 . Particularly as respects the front body  16   a  of the upper magnetic pole of the magnetic core  16 , the accuracy of positioning thereof can be markedly improved because the trench  29   a  destined to serve as the site for formation of the front body  16   a  of the magnetic pole is shaped in a state devoid of difference of level. Since the front body  16   a  of the magnetic pole is formed by embedding the magnetic material by means of the collimation sputter within this trench  29   a , the front body  16   a  of the magnetic pole can be obtained with high quality without entrapping voids therein in a highly accurately positioned state. 
     Further, the magnetic pole proper  14   a  and the front body  16   a  of the magnetic pole can be heat-treated at elevated temperatures up to about 500° C. because they are wholly formed of an inorganic material excelling in resistance to heat and further because they are completely formed prior to the formation of the insulating layer  18  in which the coil  19  is to be embedded. AS a result, the magnetic member having a high saturation flux density can be vested with uniaxial anisotropy which is prone only to insignificant dispersion. 
     In the upper magnetic core  16  of the thin-film magnetic head of the embodiment described above, it is optional with the manufacturer to have the front body  16   a  of the magnetic pole and the rear body  16   b  of the magnetic pole formed with mutually different magnetic materials. By using a material having a higher saturation flux density or a material having a larger anisotropy of induced magnetism for the front body  16   a  of the magnetic pole, for example, the recording on a magnetic recording medium of high coercive force can be facilitated and the thickness of the magnetic layer in the front part can be decreased. As a result, the desire to diminish the amount of side fringing can be satisfied. Further by setting the anisotropic magnetic field H k  of the front body  16   a  of the magnetic pole at a high level, and at the same time, setting the anisotropic magnetic field H k  of the rear body  16   b  of the magnetic pole at a low level, magnetic resistance offered by the magnetic path can be decreased and the head efficiency can be exalted. 
     The embodiment described above represents a case of embedding the magnetic material by means of sputter in the trench formed in advance by RIE. It is optional with the manufacturer to form a film of the magnetic material, shape the film of the magnetic material as by ion milling or RIE, and then form the insulating layer and perform the work of polishing back thereon as usually practiced. In this case, however, the accuracy of track width is more or less degraded. 
     Embodiment 6 
     The thin-film magnetic head according to this embodiment is a thin-film magnetic head which is provided with such an embedded magnetic pole as shown in FIG.  1  and is characterized in that a trench in which a magnetic pole is embedded has lateral walls having a taper of at least two steps. First, this thin-film magnetic head will be described below with reference to one example of the process of production shown in FIGS. 24A,  243 , and  24 C. 
     First, as shown in FIG. 27A, the insulating film  12  made of Al 2 O 3 , the etching stopper  13  made of Al 2 O 3 , or C, an insulating layer  23   a  made of SiO 2 , an insulating layer  23   b  made of a sputtered SiO 2  film, a polishing stopper layer  25  made of Al 2 O 3 , an etching mask  26  made of C or Si, and an insulating layer  27  made of SiO 2  are superposed on the substrate  11 . In this case, the insulating layer  27  is destined to serve as stock for cutting in the subsequent polishing operation. 
     Then, as shown in FIG. 27B, after the formation of a resist mask (not shown), the insulating layer  27  is etched with such a gas as CF 4 , then the etching mask  26  with such a gas O 2 , subsequently the polishing stopper layer  25  with such a gas as Ar-containing CF 4 , and finally the insulating layer  23   a ,  23   b  with such a gas as CF 4  invariably by means of RIE, for example. Thus, the resist mask is removed and the trench is completed. At this time, owing to the presence of the etching mask  26 , the upper parts of the lateral walls defining the trench can be cut vertically. By controlling such etching conditions as the temperature of the substrate, the lateral walls can be converged or diverged to a certain degree in the direction of depth of the trench. Further, owing to the presence of the etching stopper  13 , the relevant films can be excessively etched to suit the occasion. Further, by properly selecting the gases to be used for etching the insulating layer  23   a  and the insulating layer  23   b  both in terms of kind and quantity so that the former layer  23   a  may be etched at a lower speed than the latter layer  23   b , the tapering angle of the trench near the bottom parts of the lateral walls of the trench can be decreased from the tapering angle of the trench at the other parts of the lateral walls to impart the lateral walls having a taper of substantially two steps to the trench. 
     Then, as shown in FIG. 27C, the laminated magnetic layer having two layered structure is deposited as by means of the collimation sputter and then the extraneous remnant, if any, from the sputtering is removed by polishing to complete the magnetic pole proper  14   a  of the lower magnetic core  14  in the embedded state. In this case, the magnetic properties of the edge part of the embedded magnetic film are easily controlled when a proper radius of curvature was left in the bottom edges of the trench in the preceding step. 
     Here, FIGS. 28 and 29 illustrate with a model the manner n which a trench is embedded with a magnetic material in the above embodiment. FIG. 28 illustrates the manner in which the trench having an ordinary one step taper, and FIG. 29 illustrates the manner in which the trench having substantially two steps taper. 
     As illustrated in the figures, by embedding the magnetic material in the trench having the lateral walls having two-step taper, the gross porosity which would otherwise occur during the collimation sputtering can be thoroughly precluded in the resent embodiment. 
     Then, after the formation of the magnetic gap on the magnetic pole proper  14   a , the insulating layer, the polishing stopper layer, and the insulating layer as stock for cutting are formed in the same manner as in the process of the above embodiment except forming the trench having lateral walls of two-step taper and the resist mask is formed. 
     Then, the insulating layer, the polishing stopper layer, and the insulating layer mentioned above are etched in order and the resist mask is removed to complete the trench. 
     Further, the laminated magnetic layer having two-layer structure is deposited in the trench as by means of the collimation sputter and the extraneous remnant, if any, from the sputtering is removed by polishing to complete the embedment of the front body  16   a  of the magnetic pole of the upper magnetic core  16  and the rear auxiliary body of the magnetic pole of the lower magnetic core. 
     Further, the insulating layer having the coil embedded therein, the rear auxiliary body of the magnetic pole of lower magnetic core, and the protective layer are formed to complete the formation of the electromagnetic transducer of the magnetic head of the present invention. 
     In accordance with the construction and the method of production described above, the otherwise possible occurrence of gross porosity during the embedment of the magnetic material as by collimation sputter can be perfectly precluded by forming the trench having the lateral walls of substantially two-step taper, namely in a smaller angle near the bottom parts of the lateral walls defining the trench than at the other parts of the lateral walls. 
     Further, as respects the dimensions of the two-step taper, let A stand for the width of the trench, B for the depth thereof, t1 for the thickness of the insulating layer of the lower layer, t2 for the thickness of the insulating layer of the upper layer, φ for the angle of taper in the lower layer, and θ for the angle of taper in the upper layer as shown in FIG. 29, and the affect of the impartation of the two-step taper will be recognized when the conditions of 0°&lt;φ&lt;88° and φ&lt;θ are satisfied without reference to the other dimensions. The impartation of the two-step taper or the impartation of bottom corners of a radius of curvature is easily attained when the condition of t1&gt;0.01×t2 is satisfied. Further, more effect is also recognized to exist under the condition, t1&gt;α 2 ×0.01×t2, wherein α stands for B/A. 
     More further, FIG. 30 is a model diagram depicting the result of embedding the magnetic film by collimation sputter in a trench of three-step taper as an applied embodiment of this invention. In this case, owing to the presence of the taper angle ψ of the third step, the length L of the converging walls in the C part or the film can be increased with the progress of the formation of the film by merely applying a substrate bias of about 0.1 W/cm 2  during the formation of the film. In consequence of this increase of the length L, the prevention of the occurrence of the gross porosity is further facilitated because the speed of film formation on the bottom surface of the trench can be maintained in spite of the progress of the film formation. 
     Further, the damage inflicted on the film by ion bombardment can be decreased because the substrate bias necessary for the prevention of the occurrence of gross porosity can be reduced. This effect is particularly conspicuous during the embedment of an amorphous film which is susceptible of crystallization. The amorphous state of the magnetic film for embedment can be kept intact because the occurrence of the gross porosity is prevented with a low substrate bias. When the ratio in atomic percentage of Co:Zr:Nb in the alloy of CoZrNb is 88:5:8 and the film-forming speed is about 200 A/min., the film undergoes partial crystallization and has the antimagnetic force thereof raised approximately to 0.5 oersted at a substrate bias of about 0.2 W/cm 2 . By imparting a three-step taper to the trench, the film is enabled by a substrate bias of not more than about 0.1 W/cm 2  to acquire an effect equivalent to what is otherwise obtained with a substrate bias of not less than 0.2 W/cm 2  and the film can be completely prevented from crystallization. As respects the thickness t3 of the added layer, the effect of this layer is discernible when this thickness is at least 0.05 μm. 
     The formation of this trench of three-step taper can be implemented by first carrying out chemical dry etching (CDE) in the initial stage of the trench etching operation and then performing RIE in the same manner as in the method described above. And the impartation of the taper angle ψ of the third step can be rendered easy by using a material such as Si 3 N 4  as the raw material for the insulating layer to which the third step of taper is to be formed. 
     Embodiment 7 
     This embodiment concerns a thin-film magnetic head in which the front body of a magnetic pole of an upper magnetic core is manufactured by a procedures comprising the steps of embedding a magnetic material as by the collimation sputter in a trench formed as of SiO 2  and then removing the extraneous remnant, if any, from the sputtering by polishing or etching back. The trench mentioned above is tapered with a smaller angle near the upper parts of the lateral walls defining the trench than the remaining parts of the lateral walls excluding the parts near the upper edges parts of the lateral walls. 
     Namely, in this embodiment, both front parts of the magnetic pole of an upper magnetic core and a lower magnetic core are formed by embedding in a trench having lateral walls of two-step taper, a taper angle near the bottom parts of the lateral walls of the trench in the lower magnetic core is provided to be smaller than that of the other parts of the lateral walls excluding the parts near the bottom parts, and a taper angle near the upper edge parts of the lateral walls of the trench in the upper magnetic core is smaller than that of the other parts of the lateral walls excluding the parts near the upper edge parts. 
     The method for the production of the thin-film magnetic head of the present embodiment will be explained below with reference to FIGS. 31A,  31 B,  31 C,  31 D, and  31 E. 
     First, an insulating layer  12  made of Al 2 O 3  and an insulating layer  23  made of SiO 2  sputter are superposed on a substrate  11 . After the subsequent formation of a resist mark (not shown), an insulating layer  23  mentioned above is etched with such a gas as CF 4 . The trench mentioned above is further etched, with the substrate temperature kept as such a low level as about 273 K, and consequently tapered with a smaller angle near the bottom parts of the lateral walls defining the trench than at other parts of the lateral walls. 
     Then, after a magnetic film is deposited in the trench by the collimation sputter, and extraneous remnant is removed by polishing, and the magnetic pole proper  14   a  of the lower magnetic core  14  is formed by embedding, as shown in FIG.  31 A. At this time, the possible occurrence of a gross porosity during the collimation sputter is also recognized as Embodiment 6. Thus, the embedment of the magnetic material in the trench having the lateral walls of two-step taper shows a good result, as shown in FIG.  29 . 
     Thereafter, as shown in FIG. 31B, a magnetic gap  15  and an insulating layer  17  are formed, a resist mask (not shown) is formed, and the insulating layer  17  mentioned above is etched to form a trench. In this case, the first part of the etching operation is carried out in the CDE with such a gas as CF 4  and the remaining part thereof is carried out by RIE in the perpendicular direction. Further, the magnetic material is deposited in the trench by the collimation sputter and the extraneous remnant, if any, from the sputtering is removed by polishing to complete a front body  16   a  of the magnetic pole of the upper magnetic core and a rear auxiliary body  14   b  of the magnetic pole of the lower magnetic core in the embedded state. 
     Further, as shown in FIG. 31B, in which an insulating layer  18  is formed, a coil  19  is embedded, and a rear body  16   b  of a magnetic pole of an upper magnetic core  16  and a protective layer  20  are formed to complete the formation of an electromagnetic transducer of the magnetic head of this invention. 
     As respects the dimensions of the two-step taper, let A stand for the width of the trench, B for the depth thereof, t1 for the thickness of the insulating layer  23   a  of the lower layer, t2 for the thickness of the insulating layer  23   b  of the upper layer, and φ for the angle of taper in the upper layer as shown in FIG. 32A, and the effect of the impartation of the two-step taper produced in precluding the occurrence of a gross porosity will become conspicuous when the t1/A is less than 2 without reference to the other dimensions. The effect is also obtained under the condition of 0°&lt;φ&lt;45°. 
     Further, FIG. 32B represents a trench of two-step taper as another applied embodiment of this invention. It is clearly noted from the diagram that an overhang from the part C is repressed and the condition of embedment is further improved. 
     FIG. 33 shows the dependency of the relative magnetic permeability of the magnetic layer having a stripe-shape which is embedded in the trench of two-step taper as shown in FIG.  32 A and has a thickness B of 2 μm, a length of 8.5 mm on φ a width of A μm. As shown in this FIG. 33, the relative magnetic permeability decreases as the width decreases, but the relative magnetic permeability in case of smaller width i.e. narrower track width significantly increases as the angle of taper decreases. 
     Further, FIG. 34 shows the recording efficiency in such thin film magnetic head when the angle of taper is varied. As clearly shown in thin FIG. 34, the recording efficiency increases as the angle of taper decreases. At this time, the front body of the magnetic pole of the upper magnetic core has a depth of 3 μm and a track width of 2 μm. 
     The embodiments thus far described represent cases of using independently the thin-film magnetic head of this invention. For example, the thin-film magnetic head of this invention may be used as an exclusively recording head and a regenerating head as of a MR element (such as, for example, a laminate) may be formed separately thereof. 
     As described above, this invention is capable of producing a thin-film magnetic head which enables the axis of easy magnetization of the leading end part of a magnetic pole to be stably oriented in the direction of track width and also permits incorporation therein of a narrow track simultaneously fulfilling both dimensional tolerance and adaptability for mass production. Thus, thin-film magnetic heads of narrow tracks which have high quality enough to operate with a high recording density up to 10 Gb/inch 2 , for example, can be produced with high repeatability and high efficiency. 
     Embodiment 8 
     FIG. 46 shows an outline of the structure of a conventional thin-film magnetic head as a recording magnetic head.  118  stands for a lower magnetic pole. On the lower magnetic pole  118 , an upper magnetic pole  121  is formed through a recording magnetic gap  120 . An air bearing surface (medium facing surface) of the upper magnetic pole  121  has a shape corresponding to a track width, and the width of upper magnetic pole  121  is spreads in a fan-shape from the neighbor area of the air bearing surface to the rear portion. In the upper magnetic pole  121  having this shape, if the width of the air bearing surface is narrowed to attain a narrow track, a magnetic saturation occures at a neck portion  125  connecting the neighborhood of the air bearing surface to the rear portion. Therefore, it becomes impossible to generate a large magnetic field. 
     Further, FIG. 47 shows a perspective view illustrating an example of a T-shaped magnetic pole structure in the neighborhood of an air bearing surface of a thin film magnetic head. The thin-film magnetic head of FIG. 47 is configured by constructing at least one of the magnetic poles  121  into a front part  123  of a magnetic pole contacting with the magnetic gap  120  and a rear part of a magnetic pole (auxiliary magnetic pole)  124 , which has a wider width than the front part  123 , in the neighborhood of the air bearing surface. Thus, the magnetic pole  118  in the neighborhood of the air bearing surface has a T-shape. Due to this T-shape structure, the portion of the magnetic pole in the neighborhood of the air bearing surface and the rear part of the magnetic pole can be connected with the auxiliary magnetic pole having a wider width. Thereby, it can suppress the magnetic saturation at the neck portion, which is produced in the magnetic head of FIG.  46 . Further, this structure is effective to attain a narrow track. 
     However, with respect to the T-shape magnetic pole in the neighborhood of the air bearing surface, the inventors found that unnecessary information had been recorded into a track side region of the recording medium by the leakage flux from edge portions  124   a  of the auxiliary magnetic pole  124 , as a result of eager studies. FIG. 48 shows a part of the results. 
     FIG. 35 is a diagram illustrating the construction of the essential part of a thin-film magnetic head which is applied to a recording-reproducing separate type magnetic head using a magnetoresistance effect element according to Embodiment. FIG. 35 shows a partially sectioned perspective view schematically illustrating the construction of the thin-film magnetic head. In FIG. 35,  111  stands for a substrate such as Al 2 O 3  TiC having a Al 2 O 3  layer. On the substrate  111 , a lower magnetic shield layer  112  having a thickness of about 1 to 3 μm and made of soft magnetic material such as a NiFe alloy or an amorphous CoZrNb alloy is formed. On this lower magnetic shield layer  112 , a magnetoresistance effect film (MR film)  114  as a reproducing element portion is formed through a lower reproducing magnetic gap  113  having a thickness of about 150 nm and made of non-magnetic insulating material such as Al 2 O 3 . In this FIG. 35,  115  stands for a lead electrode for supplying a sense current to the MR film. 
     On the MR film  114  and the lead electrode  115 , an upper magnetic shield layer  117  made of a soft magnetic material like the lower magnetic shield layer  112  is formed through an upper reproducing magnetic gap  116  made of a non-magnetic insulating material like the lower reproducing magnetic gap  113 . Thereby, a shield type MR head  118  is constructed. 
     On the above shield type MR head  118 , a thin-film magnetic head  119  is formed as a recording head. A lower recording magnetic pole of the thin-film magnetic head  119  is constructed with the same material as the magnetic layer of the upper magnetic shield layer  117 . That is, the upper magnetic shield layer  117  of the shield type MR head  118  is also used as the lower recording magnetic pole of the thin-film magnetic head  119 . On the lower magnetic recording pole  117  used also as the upper magnetic shield layer, a recording magnetic gap  120  composed of non-magnetic insulating material such as Al 2 O 3 . 
     On the recording magnetic gap  120 , an upper recording magnetic pole  121 , in which a portion around an air bearing surface (medium facing surface) of the thin-film magnetic is composed of a front part  123  and a rear part  124  having a greater width than the front part  123 , is provided. At the rear side of the front part  123  of the upper magnetic pole  121  which is opposed the air bearing surface, a coil  122  composed of Cu buried in an insulating layer formed of polyimide or the like (not shown) is formed under the rear part  124  extended from laminated portion with the front part  123  that is, between the rear part  124  of the upper of the upper. magnetic pole  121  and the lower magnetic pole  117 . Thus, the essential parts of the thin-film magnetic head  119  as a recording head are constructed. 
     Next, we will describe the portion around the air bearing surface of the recording magnetic poles  117  and  121  below with reference to FIGS. 36 and 37. 
     In a portion in the neighborhood of the air bearing surface of the upper recording magnetic pole  121 , the front part  123  of the magnetic pole which is disposed on a side of the recording magnetic gap  120  and contacts with the recording magnetic gap  120  with a prescribed track width Tw, and the rear part  124  which is disposed on an upper side of the front part  123  of the magnetic pole and has a greater width than the front part  123 , as shown in FIGS. 36 and 37. Namely, the portion in the neighborhood of the air bearing surface of the upper recording magnetic pole  121  constructs a T-shaped magnetic pole. 
     Further, regions  124   a  including corner portions of the rear part of the magnetic pole which are on a side of the recording magnetic gap  120  are recessed from the air bearing surface (medium facing surface) as shown by the arrow line in FIG.  36 . The corner portions  124   a  recessed from the air bearing surface are, for example, the regions having an angle of with respect to the track width direction. 
     The corner portions  124   a  mentioned above have a recessed distance from the air bearing surface of, preferably, 0.05 μm or more. For example, in the conventional T-shaped magnetic pole having corner regions which are not recessed from the air bearing surface, a magnetic field intensity from. the corner portions is about 1000 to 3500 Oe. In contrast, if the corner portions  124   a  is recessed about 0.1 um from the air bearing surface, the magnetic field intensity is attenuated to less than 500 Oe. Thus, by suppressing the leakage flux from the corner regions  124   a  on a side of the recording magnetic gap  120  of the rear part  124  of the magnetic pole, the excessive information-recording flowing into the track-side region of the recording medium from the rear part  124  of the magnetic pole is greatly suppressed. 
     The recess of the corner portions  124   a  of the rear part  124  of the magnetic pole from the air bearing surface can be achieved, for example, by trimming the regions having an angle θ with respect to the track width direction from the air bearing surface with an ion-milling process and the like. FIGS. 36 and 37 show the state in which only corner regions  124   a  are recessed. This shape can be achieved by substantially realizing an etching tolerance 0 using an FIB (forced ion beam etching) method for trimming. 
     As the trimming process of the corner portions  124   a , a conventional PEP (photoengrave process) and the ion-milling process can be used. However, in the case of applying the PEP in the trimming process, an alignment accuracy (alignment tolerance Δ) of an exposure machine poses a problem. Generally, the alignment toleranceΔ is 0.2 um or more. When an angle θ of the corner portions  124   a  is 45 degree, the width of the rear part  124  must be greater than the width of the front part  123  with an increased width of 4Δ, because there is a possibility that the etching comes to the front part  123 . Therefore, the width of the rear part  124  is desirable to be greater than the width of the front part  123  with the increased width of 2Δ (1+cot θ) or more. Further, in a wafer process, the rear part  124  of the magnetic pole has also an alignment tolerance of about 1 to 0.1 um to the front part  123  of the magnetic pole. Thus, actually the width of the reart part  124  of the magnetic pole must be sat to be further greater with an increased width of 1Δ. 
     For example, the upper recording magnetic pole  121  in FIGS. 36 and 37 is formed by the steps of producing a magnetic pole structure having the front part  123  and rear part  124  of the magnetic pole in the wafer process, cutting at the air bearing surface and polishing the magnetic pole structure, and trimming the corner regions  124   a.    
     The T-shaped magnetic pole having the front part  123  and the rear part  124  is formed in the wafer process, for example, by the following procedures: 
     First, a magnetic material is buried by a sputtering method or the like in a trench  126  formed in an insulating layer  125  formed of SiO x  or the like, and the front part  123  of the magnetic pole is formed. Next, an upper surface of the front part  123  is flattened, and then the rear part  124  of the magnetic pole is laminated, thereby the T-shaped magnetic pole is obtained. 
     In this embodiment mentioned above, an example that only the upper recording magnetic pole  121  is formed as the T-shaped magnetic pole is described. It is possible to form a lower recording magnetic pole  117 , which opposes to the upper recording magnetic pole  121  through the recording magnetic gap  120 , as a T-shaped magnetic pole having a protrusion to the recording magnetic gap  120 , as shown in FIG.  38 . For example, by etching about 0.5 um. width of the lower recording magnetic pole with keeping a width corresponding to the track width, the lower recording magnetic pole  117  which has a front part  127  of the magnetic pole protruding to an upper direction and a rear part  128  of the magnetic pole having a greater width than the front part  127  can be obtained. 
     In this case, it is desirable that in the rear part  128  of the magnetic pole of the lower recording magnetic pole  117 , regions  128   a  opposed to the corner regions  124   a  of the rear part  124  of the upper recording magnetic pole  121  is recessed from the air bearing surface. Thereby, it is possible to go back the arrival points of leakage flux from the corner regions  124   a  of the rear part  124  of the upper recording magnetic pole  121 . As a result, a leakage flux at the air bearing surface can be weakened. 
     Further, it is effective in order to decrease the leakage flux that a shape of the corner regions  124   a  of the rear part  124  of the upper recording magnetic pole  121 , which are recessed from the air bearing surface, is formed as a curved shape, as shown in FIG.  39 . By forming a shape of the corner portions  124   a  to the curved shape, it becomes possible to prevent the concentration of magnetic flux. Thereby, the leakage flux from the corner portions  124   a  and the neighborhood thereof can be decreased. 
     In FIGS. 38 and 39, E stands for regions for trimming. In case that a combination of conventional PEP and ion milling method is carried out, it is desirable to conduct trimming regions which include the corner portions  124   a  of rear part  124  of the upper recording magnetic pole  121  (opposed corner regions  128   a  of the rear part  128  of the lower recording magnetic pole  117 ) and in consideration of cross of alignment mentioned above. 
     Embodiment 9 
     Next, we will describe Embodiment 9 of the thin-film magnetic head. 
     FIGS. 40 and 41 illustrate a magnetic pole structure of Embodiment 9. In FIGS. 40 and 41, portions of an upper recording magnetic pole  121  around an air bearing surface are the same as those of the Embodiment 8. That is, the magnetic pole structure has a front part  123  of the magnetic pole disposed on a side of a recording magnetic gap  120  and contacting the recording gap  120  with a prescribed track width Tw, and a rear part  124  of the magnetic pole disposed on the front part  123  and having a greater width than the width of the front part  123  of the magnetic pole. 
     Further, a portion  123 A of the front part  123  which contacts the rear part  124  on an opposite side to the recording magnetic gap  120  and the rear part  124  of the magnetic pole are recessed from the air bearing surface. Such recess of the rear part  124  of the magnetic pole and the portion  123 A of the front part  123  which contacts the rear part  124  on an opposite side to the recording magnetic gap  120  can be obtained by trimming from the air bearing surface side, as the Embodiment 8. It is desirable to select a recessed distance to the same degree as that of Embodiment 8. 
     In this case, when the portion  123 A of the front part  123  on a side of the rear part  124  of the magnetic pole is trimmed together with rear part  124  of the magnetic pole, an alignment accuracy (alignment tolerance Δ) of an exposure machine also poses a problem. Generally, the alignment toleranceΔ is 0.2 um or more. On the other hand, a height h 0  of the portion  123 B, which is at the air bearing surface of the front part  123  of the magnetic pole, is the lowest height which is required to generate a sufficient amount of magnetic flux to write into a medium. The height h 0  of the portion  123 B at the air bearing surface is about 0.3 um. Therefore, the height h of the front part of the magnetic pole is desirable to be (h 0 +2Δ) or more, in order to be coexist with the recording magnetic field intensity and the decrease of the leakage flux from the rear part  124  of the magnetic pole. Concretely, since the h 0  is about 0.3 um and Δ is 0.2 um or more, the height h of the front part  123  of the magnetic pole is desirable to satisfy the formula h≧0.7 um. 
     As mentioned above, by recessing the rear part  124  of the magnetic pole and the portion  123   a  of the front part  123  on a rear part  123  side from the air bearing surface, the leakage flux from the rear part  124  of the magnetic pole can be suppressed. Thus, an excess information recording by the rear part  124  of the magnetic pole into the track side region of the recording medium can be greatly suppressed. 
     Embodiment 10 
     FIG. 42 illustrates the embodiment of a thin-film magnetic head of Embodiment 10. 
     In the magnetic pole structure shown FIG. 42, portions of an upper recording magnetic pole  121  in the neighborhood of an air bearing surface are the same as those of the Embodiment 8. That is, the magnetic pole structure has a front part  123  of the magnetic pole disposed on a side of a recording magnetic gap  120  and contacting the recording gap  120  with a prescribed track width Tw, and a rear part  124  of the magnetic pole disposed on the front part  123  and having a greater width than the width of the front part  123  of the magnetic pole. Further, the rear part  12 A of the magnetic pole is recessed from the air bearing surface. It is desirable to substantially select the recessed distance nearly equal to that of Embodiment 8. 
     In this embodiment, the front part  123  of the magnetic pole is composed of a different magnetic material from the rear part  124  of the magnetic pole. For example, the rear part  124  is formed of a magnetic material having a lower hardness than a magnetic material of the front part  123 . By applying such combination of magnetic materials, it becomes possible that only the rear part  124  can be recessed from the air bearing surface owing to the difference of polishing amounts based on the difference of hardness of the magnetic materials, when the air bearing surface of the thin-film magnetic head is polished. 
     For example, when a high saturation magnetization material such as Ni 50 Fe 50  (at ) is used a material of the front part  123  of the magnetic pole and a magnetic material such as an amorphous CoZrNb is used a material of the rear part  124  of the magnetic pole, the recessed distance of the rear part  124  based on the difference of the polishing amount can be attained to about 0.05 to 0.1 um. According to this process, it becomes unnecessary to conduct the PEP or FIB process with respect to the air bearing surface. Hence, the mass productivity of the thin-film magnetic head is greatly improved. 
     Further, when a CMP method is applied to the polishing process of the air bearing surface of the thin-film magnetic head, this embodiment has the following effect. That is, when a magnetic material having higher melting property than a magnetic material for the front part  123  is used as the material of the rear part  124 , the recess amount of the rear part  124  of the magnetic pole can be easily controlled using the difference of the melt-ability. As a concrete example of the combination of materials of front part  123  and rear part  124 , the combination of Ni 50 Fe 50  (at ) and CoZrNb is exemplified. 
     As mentioned above, since the front part  123  and the rear part  124  are composed of different magnetic material layers each other, and the rear part  124  is recessed from the air bearing surface based on the difference in the hardness or in the melting property in the material layers, it is possible to suppress the leakage flux from the rear part  124  without conducting the PEP process or the FIB process. Therefore, an excess information recording by the rear part  124  of the magnetic pole into the track side region of the recording medium can be greatly suppressed. At the same time, the mass productivity of the thin-film magnetic head is greatly improved. 
     Embodiment 11 
     In the magnetic pole structure shown FIG. 43, portions of an upper recording magnetic pole  121  in the neighborhood of an air bearing surface are the same as those of the Embodiment 8. That is, the magnetic pole structure has a front part  123  of the magnetic pole disposed on a side of a recording magnetic gap  120  and contacting the recording gap  120  with a prescribed track width Tw, and a rear part  124  of the magnetic pole disposed on the front part  123  and having a greater width than the width of the front part  123  of the magnetic pole. 
     Further, corner portions  124 A of the rear part  124  on a side of the recording magnetic gap  120  are chamfered to the R-shape (R-chamfered shape), respectively. This R-shape of the corner portions  124 A is desirable to have a radius of curvature of 0.3 um or more. Here, an excess information recording produced by the leakage flux from the rear part  124  of the magnetic pole is caused by concentration of magnetic flux at the corner portions of the rear part  124  of the magnetic pole. Therefore, by shaping the corner portions  124 A of the rear part  124  on a side of the recording magnetic gap  120  to the R-shape and by relaxing the concentration of magnetic flux, the excess information recording from the rear part  124  of the magnetic pole into the track side region of the recording medium can be greatly suppressed. 
     The magnetic pole structure illustrated in FIG. 43 can be formed, for example, by the following processes. 
     First, in a trench  126  in an insulating layer  125  composed of SiOx and the like, a magnetic material is buried and filled by, for example, sputtering to form the front part  123  of the magnetic pole. Further, the insulating layer  125  is shaped to a height so that a part of the rear part  124  of the magnetic pole is buried therein, and corner portions of the insulating layer  125  corresponding to the corner portions  124 A of the rear pare  124  of the magnetic pole on a side of the recording magnetic gap  120  are processed by chemical etching and the like to form a curved shape. By sputtering on the insulating layer  125  including the corner portions of the insulating layer  125 , the rear part  124  of the magnetic pole which has the R-shaped corner portions  124 A is obtained. 
     According to the Embodiments 8-11, the recording-reproducing separate type magnetic head suitable for the narrower track can be realized. Further, in case that the width of the rear part of the magnetic pole is wider than the width of the front part of the magnetic pole like the present invention, a wide margin in combination with the magneto-resistance effect element having the height dependency of output can be obtained, because a throat-height dependency of recording characteristic such as an OW characteristic becomes gentle. Thereby, the high yield of the production of the recording-reproducing magnetic head can be increased. 
     As mentioned above, an excess information recording from the rear part of the T-shaped magnetic pole into the track side region of the recording medium can be prevented. Therefore, in case of a high-density recording, an excellent recording characteristic can be obtained. 
     Next, we will describe more other embodiments of the present invention. 
     Embodiment 12 
     FIG. 44 shows a cross section of an example of a T-shaped magnetic pole of the present invention. In FIG. 44,  123  stands for a front part of a magnetic pole,  124  stands for a rear part of a magnetic pole,  124 ′ stands for an intermediate part of a magnetic pole. In this embodiment, the intermediate part  124 ′ as a part of the rear part  124  is used for explaining. 
     FIG. 45A illustrates an example of this embodiment. After forming a lower magnetic pole  118  and a magnetic gap  120 , a front part  123  of an upper magnetic pole  119  and a rear part  124  of the upper magnetic pole  119  were formed. Then, the corner portions on a side of the magnetic gap layer was trimmed from the air bearing surface by the FIB method to form an intermediate part  124 ′. Here, when a trimming depth dt from the air bearing surface is small, the magnetic field intensity at the position of the recording medium is not be sufficiently decreased. Thus, the trimming depth dt was set 0.05 um or more. 
     The trimming of corner portions can be carried out to a rising part  124   d  of the upper magnetic pole shown in FIG.  35 . In this case, since an area facing the magnetic gap  120  is decreased and an amount of magnetic flux which returns within a deep gap is decreased, the recording magnetic flux intensity can be increased. 
     FIG.  45 A′ is an example in which the lower magnetic pole  118  is processed so as to be a protruding shape having nearly a track width. In this example, since an intensity distribution in a track width direction becomes sharp, it is profitable for attaining a narrower track width. 
     FIG. 45B illustrates another example of this embodiment. Similarly, after forming the lower magnetic pole  118  and the magnetic gap layer  120 , a film formed of a material such as SiOx is formed thereon. Then, a trench is formed in the film by using a RIE method or the like. As shown in FIG. 45C, after forming a resist frame, a film of a material such as NiFe is formed by plating. In this example, the front part  123  and the rear part  124  of the upper magnetic pole are formed as one body at the neighborhood of the air bearing surface. Thereafter, the trimming of corner portions  124   a  of the rear part  124  is carried out from the air bearing surface. Thereby, similar effects are obtained as the example shown in FIG.  45 A. 
     The film-forming of the upper magnetic pole  119  can also obtained by sputtering and the like. In this case, when the trench portion is formed with a two-step, as shown in FIG. 45D, the film-forming of the upper magnetic pole can be carried out at one time to form the upper magnetic pole as shown in FIG.  45 B. Thus, the structure of the magnetic pole in this embodiment, enables to form the upper magnetic pole  119  en bloc without separating into the front part  123  and the rear part  124 . 
     The embodiment shown in FIGS. 45B can apply to the lower magnetic pole  118  which has a protruding shape having nearly a track width. Similarly, since an intensity distribution in a track width direction becomes sharp, it is profitable for attaining a narrower track width. 
     FIGS. 45E and 45F illustrate further other examples of the present invention. FIG. 45E shows a separate type in which the front part and the rear part are as separate members. And FIG. 45F shows one bloc type. In these examples, like the above examples shown in FIG. 45A, after forming upper and lower magnetic poles, a front part  123  and a rear part  124  of the upper magnetic pole  119  were formed. Then corner portions  124   a  were trimmed so as to have a R-shape. Since the edge portions (corner portions) are formed to be round and have tot sharp edges, it became possible to suppress the concentration of magnetic flux. Therefore, the leakage flux from the edge portions is greatly decreased. 
     Embodiments shown in FIGS. 45E and 45F can apply to the lower magnetic pole  118  which has a protruding shape having nearly a track width. Similarly, since an intensity distribution in a track width direction becomes sharp, it is profitable for attaining a narrower track width. 
     FIGS. 45G and 45H illustrate also further other examples of the present invention. FIG. 45H shows a separate type in which the front part and the rear part are as separate members. And FIG. 45G shows one bloc type. In these examples, after forming the lower magnetic pole  118  and the magnetic gap layer  120 , a film formed of a material such as SiOx is formed thereon. Then, a trench is formed in the film by using a RIE method or the like, as shown in FIG.  45 G′. Further, when a second recess having a second step is formed, an etching process is carried out to have a round edges in the bottom of the recess by changing an etching condition (FIG.  45 G″). By forming a film formed of a magnetic material in the two-stepped trench. Thereby, a T-shaped upper magnetic pole having round bottom corners in the upper step having a wider width can be formed. Owing to this structure having no sharp corners in the edge portions, it is possible to suppress the concentration of the magnetic flux. Thereby, an excess write into the recording medium from the edge portions can be prevented. 
     Embodiments shown in FIGS. 45G and 45H can apply to the lower magnetic pole  118  which has a protruding shape having nearly a track width. Similarly, since an intensity distribution in a track width direction becomes sharp, it is profitable for attaining a narrower track width. 
     As mentioned above, unnecessary information recording from the rear part of the T-shaped magnetic pole into the track side region of the recording medium can be prevented. Therefore, in case of a high-density recording, an excellent recording characteristic can be obtained.