Patent Publication Number: US-2005128928-A1

Title: Recording / reproducing head, recording / reproducing head array, method of producing the same, and recording apparatus and reproducing apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a recording/reproducing head for recording and reproducing polarization information recorded on a dielectric substance, such as a ferroelectric recording medium, as well as a recording/reproducing head array, a method of producing the recording/reproducing head, and a recording apparatus and a reproducing apparatus which use the recording/reproducing head.  
      2. Description of the Related Art  
      A technique of a recording/reproducing apparatus which uses SNDM (Scanning Nonlinear Dielectric Microscopy) for nano-scale analysis of a dielectric recording medium is suggested by the inventors of the present invention. In SNDM, it is possible to increase its resolution associated with the measurement to sub nanometer resolution, by using an electric conductive cantilever (or probe) with a small probe mounted on its tip, which is used for AFM (Atomic Force Microscopy) or the like. Recently, the development of a super high density recording/reproducing apparatus has been advanced, wherein the apparatus records data onto a recording medium having a recording layer made of a ferroelectric material, by using the technique of SNDM (refer to Japanese Patent Application Laying Open NO. 2003-085969).  
      The recording/reproducing apparatus of this type which uses SNDM reproduces information by detecting a positive or negative direction of polarization of the recording medium. This is performed by using a change in an oscillation frequency of a LC oscillator, which includes (i) a high frequency feedback amplifier including an L component, (ii) a conductive probe mounted on this amplifier, and (iii) a capacitance Cs of the ferroelectric material under the probe, caused by a change ΔC in a small capacitance due to a non-linear dielectric constant which have origin in the distribution of the positive and negative of the polarization. Namely, it is performed by detecting the change in the distribution of the positive and negative of the polarization, as a change Δf in the oscillation frequency.  
      Moreover, by applying an alternating electric field whose frequency is sufficiently low with respect to the oscillation frequency in order to detect a difference in the positive and negative of the polarization, the oscillation frequency is changed along with the alternating electric field, and the rate of change in the oscillation frequency including its sign is determined by the non-linear dielectric constant of the ferroelectric material under the probe. Then, by FM (Frequency Modulation)-demodulating and extracting a component due to the alternating electric field, from a high-frequency signal of the LC oscillator which is FM-modulated in accordance with the change in the small capacitance ΔC along with the application of the alternating electric field, the record information (data) recorded on the ferroelectric recording medium is reproduced.  
     SUMMARY OF THE INVENTION  
      The record and reproduction of the record information is performed by using the probe as a recording/reproducing head. The probe can be broadly classified into a projection portion of a needle shape and a support portion for supporting the projection portion. By applying an electric field to between the projection portion and the recording medium, the information is recorded and reproduced as described above.  
      It is desirable that the support portion plays a role as a path (i.e. electricity passage) of the electric field (or an electric current) applied to the projection portion. However, there is such a technical problem that the electric filed concentrates at the support portion (i.e. a part of the support portion), which causes the electric field to be applied to between the support portion and the recording medium. The generation of the electric field between the support portion and the recording medium as described above is a source of noise in the recording/reproducing apparatus which uses the principle of SNDM in which the information is reproduced by the application of the alternating electric field, and it is disadvantageous in the appropriate record and reproduction of the information, which is also a technical problem.  
      It is therefore an object of the present invention to provide a recording/reproducing head capable of inhibiting the generation of an unnecessary electric field, as well as a recording/reproducing head array, a method of producing the recording/reproducing head, and a recording apparatus and a reproducing apparatus which use the recording/reproducing head (or the recording/reproducing head array).  
      (Recording/Reproducing Head)  
      The above object of the present invention can be achieved by a first recording/reproducing head for performing at least one of a record operation of recording information onto a dielectric recording medium and a reproduction operation of reproducing the information from the dielectric recording medium, the recording/reproducing head provided with: a support member which extends in a longitudinal direction (e.g. in a longitudinal direction of the recording/reproducing head); and a projection portion which is mounted on the support member such that a tip of the projection portion faces the dielectric recording medium, the support member having a rounded shape at a surface thereof on a side facing the dielectric recording medium, at least in a mounted portion on which the projection portion is mounted.  
      According to the first recording/reproducing head of the present invention, it is possible to prevent the application (or the generation) of an unexpected electric field (or discharge), and it is possible to stabilize the operations of recording and reproducing the information by using a recording apparatus and a reproducing apparatus described later.  
      Specifically, the first recording/reproducing head of the present invention is provided with the support member which extends in the longitudinal direction of the recording/reproducing head. It is preferable to use a material having electric conductivity as the support member, but as described later, it is possible to select an appropriate material in accordance with a resonance frequency of a resonance circuit (in other words, an oscillation frequency of an oscillator) in a reproducing apparatus. Alternatively, by selecting an appropriate material, it is also possible to change a vibration frequency obtained when the recording/reproducing head is moved along the surface of the information recording medium, as occasion demands. The projection portion is mounted on the support member such that the tip of the projection portion faces the dielectric recording medium. The projection portion may be mounted upright on the support member. The projection portion is also preferably constructed from a material having electric conductivity.  
      In particular, the first recording/reproducing head of the present invention has a rounded shape at the surface thereof on the side facing the dielectric recording medium, at least in the mounted portion on which the projection portion is mounted out of the support member. The “mounted portion” is not rigorously limited to the portion to mount the projection portion on, but also includes surrounding area portions or vicinity area portions. The “rounded shape” in the present invention indicates a relatively rounded shape, as compared to the shape of a portion not facing the dielectric recording medium, as described later, or a shape obtained by a chamfer process, for example.  
      Because the surface of the support member is rounded as described above, for example, if the support member is used for a recording apparatus or a reproducing apparatus described later, it is possible to prevent the concentration of an electric field, which is possibly generated on the surface by that the electric field for the record and reproduction operations is supplied to the first recording/reproducing head.  
      If the surface has not the rounded shape but an angular part (e.g. the cross section of the support member has a square shape), an electric field concentrates at the angular part. In the extreme case, there is a possibility that an unexpected discharge is performed between the angular part and the dielectric recording medium. Such a discharge is undesirable in a recording apparatus and a reproducing apparatus which use SNDM, for example, for changing or detecting the polarization condition of the dielectric recording medium by applying an electric field to between the recording/reproducing head (especially, the projection portion of the recording/reproducing head) and the dielectric recording medium (or a return electrode).  
      However, the use of the first recording/reproducing head hardly causes the concentration of the electric field at the support member, which is advantageous. By this, if an electric field is applied to between the recording/reproducing head and the dielectric recording medium, it is possible to realize an appropriate discharge (i.e. the application of an electric field) between the projection portion and the dielectric recording medium. By preventing the concentration of the electric field at the support member, it is possible to inhibit or remove the generation (the application) of the unexpected electric field or the like between the support member and the dielectric recording medium (or a return electrode).  
      Consequently, according to the first recording/reproducing head of the present invention, it is possible to prevent the concentration of the electric field at the support member, and it is possible to effectively inhibit or remove the generation (the application) of the unexpected electric field (or the unexpected discharge) from the support member. Therefore, it is possible to inhibit a bad influence caused by the discharge, on the surrounding of the recording/reproducing head, to thereby increase the degree of freedom in a structure in the vicinity of the recording/reproducing head (e.g. the arrangement/positions of the recording/reproducing head, the return electrode, and a plurality of recording/reproducing heads, as described later).  
      Moreover, the support member and the projection portion may be formed in one body. Namely, even if the support member and the projection portion are formed from a single material, if the support member and the projection portion can be distinguished from a difference in their shapes, then, this aspect is included in the present invention.  
      Furthermore, from the viewpoint of effectively inhibiting or removing the unexpected discharge, the support member preferably has a rounded shape at the surface thereof on the side not facing the dielectric recording medium, in the mounted portion on which the projection portion is mounted. Alternatively, the entire part of the support member may be rounded.  
      In one aspect of the first recording/reproducing head of the present invention, the support member has a relatively rounded shape at the surface thereof on the side facing the dielectric recording medium, as compared with a shape at an another surface thereof on an another side not facing the dielectric recording medium, at least in the mounted portion on which the projection portion is mounted.  
      According to this aspect, it is possible to effectively prevent the unexpected discharge which is possibly performed between the support member and the dielectric recording medium, to thereby inhibit or remove the generation (the application) of the unexpected electric field or the like.  
      In another aspect of the first recording/reproducing head of the present invention, the support member has a prism shape obtained by a chamfer process with respect to corners thereof on the side facing the dielectric recording medium, at least in the mounted portion on which the projection portion is mounted.  
      According to this aspect, the corners or angular parts are chamfered (e.g. the corners or angular parts are removed by grinding process, polishing process, peeling-off process, or the like), so that it is possible to effectively prevent the concentration of the electric field at the portion which is used to be the corner, to thereby inhibit or remove the generation (the application) of the unexpected electric field or the like.  
      In another aspect of the first recording/reproducing head of the present invention, the support member has a rounded shape at a surface thereof on an opposite side to the side facing the dielectric recording medium, or has a prism shape obtained by a chamfer process with respect to corners thereof on the opposite side, at least in the mounted portion on which the projection portion is mounted.  
      In another aspect of the first recording/reproducing head of the present invention, if a distance between the support member and the dielectric recording medium is h, a radius of the rounded shape is greater than or equal to h/10.  
      According to this aspect, by realizing the shape rounded enough to satisfy the above condition, it is possible to effectively prevent the unexpected discharge caused by the concentration of the electric field.  
      Even if the portion having the rounded shape is not simple rounded shape (e.g. the rounded shape is merely smooth surface or the rounded shape is not a pure sphere shape/a pure circle shape) and the radius thereof cannot be easily evoked or expressed, if the above condition is satisfied in full consideration of the curvature of such a smooth surface or the like, the radius thereof in the case where the smooth surface or the like is regarded as a circular arc, and the like, it is obvious that this aspect is included in the scope of the present invention.  
      The above object of the present invention can be also achieved by a second recording/reproducing head for performing at least one of a record operation of recording information onto a dielectric recording medium and a reproduction operation of reproducing the information from the dielectric recording medium, the recording/reproducing head provided with: a support member which extends in a longitudinal direction; and a projection portion which is mounted on the support member such that a tip of the projection portion faces the dielectric recording medium, the support member having a relatively rounded shape at a mounted portion on which the projection portion is mounted, as compared with a shape at an other portion of the support member except the mounted portion.  
      According to the second recording/reproducing head of the present invention, it is possible to receive the same benefits as those of the first recording/reproducing head of the present invention. Particularly, in the second recording/reproducing head, the mounted portion, on which the projection portion is mounted, is relatively rounded, as compared to the other portion on which the projection portion is not mounted. For example, the mounted portion (particularly, its planar shape) may be rounded, and the other portion, on which the projection portion is mounted, may be rectangular. Even with such a shape, at least in the mounted portion, it is possible to prevent the concentration of the electric field at the support member, to thereby inhibit or remove the generation (the application) of the unexpected electric field or the like.  
      Consequently, according to the second recording/reproducing head, it is possible to receive the same benefits as those of the first recording/reproducing head described above.  
      In one aspect of the second recording/reproducing head of the present invention, the support member has a prism shape obtained by a chamfer process with respect to corners thereof, in the mounted portion on which the projection portion is mounted.  
      According to this aspect, the corners or angular parts are chamfered (e.g. the corners or angular parts are removed by grinding process, polishing process, peeling-off process, or the like), so that it is possible to effectively prevent the concentration of the electric field at the portion which is used to be the corner, to thereby inhibit or remove the generation (the application) of the unexpected electric field or the like.  
      The above object of the present invention can be also achieved by a third recording/reproducing head for performing at least one of a record operation of recording information onto a dielectric recording medium and a reproduction operation of reproducing the information from the dielectric recording medium, the recording/reproducing head provided with: a support member which extends in a longitudinal direction; and a projection portion which is mounted on the support member such that a tip of the projection portion faces the dielectric recording medium, the support member having a rounded shape at an inhibition portion where application (i.e. generation) of an electric field between the support member and the dielectric recording medium is to be inhibited.  
      According to the third recording/reproducing head of the present invention, as in the first and second recording/reproducing head of the present invention described above, it is possible to prevent the concentration of the electric field at the support member, and it is possible to effectively inhibit or remove the generation (the application) of the unexpected electric field or the like from the support member.  
      Particularly, in the third recording/reproducing head, out of the support member, the inhibition portion where the generation (the application) of the electric field (particularly, the unexpected electric field) is to be inhibited, is rounded. Namely, by making the portion where the generation (the application) of the electric field is undesirable have a rounded shape, out of the support member, it is possible to effectively inhibit the generation (the application) of the unexpected electric field, which is advantageous. As the inhibition portion where the generation (the application) of the electric field is to be inhibited, the following is conceivable: the surface of the support member on the side facing the dielectric recording medium, the surface thereof on the side facing the return electrode, the surface thereof on the side facing adjacent recording/reproducing heads in the case of a recording/reproducing head array having a plurality of recording/reproducing heads, as described later.  
      Consequently, according to the third recording/reproducing head, it is possible to receive the same benefits as those of the first and second recording/reproducing heads described above.  
      Incidentally, even in the third recording/reproducing head, as with the first and second recording/reproducing heads described above, the inhibition portion where the generation (the application) of the electric field is to be inhibited may be relatively rounded, as compared to the other portion where the generation (the application) of the electric field is not to be inhibited, or may be rounded by performing the chamfer process.  
      In one aspect of the third recording/reproducing head of the present invention, the inhibition portion includes a surface of the support member on a side facing the dielectric recording medium.  
      According to this aspect, as described above, it is possible to effectively prevent the unexpected discharge between the support member and the dielectric recording medium.  
      In another aspect of the third recording/reproducing head of the present invention, the inhibition portion includes a surface of the support member on a side facing a return electrode, a high-frequency electric field being applied between the return electrode and the recording/reproducing head.  
      According to this aspect, it is possible to effectively prevent an unexpected electric field between the support member and the return electrode. Therefore, this increases the degree of freedom in the structure of the recording/reproducing head, such as placing the return electrode in the vicinity of the recording/reproducing head, which is advantageous. Incidentally, the return electrode will be described in detail in the preferred embodiments later.  
      In another aspect of the third recording/reproducing head of the present invention, if a distance between (i) the support member and (ii) a portion where the electric field is possibly applied to between the support member is h, a radius of the rounded shape is greater than or equal to h/10.  
      According to this aspect, by realizing the shape rounded enough to satisfy the above condition, it is possible to effectively prevent the generation (the application) of the unexpected electric filed or the like caused by the concentration of the electric field.  
      The above object of the present invention can be also achieved by a recording/reproducing head array provided with: a plurality of first, second, or third recording/reproducing heads described above (including their various aspects), the support member further having the rounded shape at a surface thereof on a side facing adjacent recording/reproducing head/heads.  
      According to the recording/reproducing head array of the present invention, even if the plurality of recording/reproducing heads are provided, it is possible to effectively prevent an unexpected discharge between the adjacent recording/reproducing heads. Therefore, it is possible to prevent the generation of noise, such as crosstalk, between the adjacent recording/reproducing heads, which enables a recording apparatus and a reproducing apparatus described above to perform the record and reproduction operations with stability. In addition, there is such an advantage that the plurality of recording/reproducing heads can be arranged densely, to thereby increase the degree of freedom in its structure.  
      (Production Method)  
      The above object of the present invention can be also achieved by a production method of producing the above-described first, second, or third recording/reproducing head (including their various aspects), the production method provided with: a mold-forming process of forming a mold for forming the projection portion and the support member; and a member-forming process of forming the projection portion and the support member by using the formed mold, the mold being formed such that, out of the mold, a portion for forming the support member has a shape corresponding to the rounded shape, in the mold-forming process.  
      According to the production method of the present invention, it is possible to the above-described first, second, or third recording/reproducing head of the present invention relatively easily.  
      Specifically, at first, in the mold-forming process, the mold for forming the recording/reproducing head is formed. Here, it is possible to form the mold by combining various processes, such as patterning by a resist and etching or the like. Particularly in the present invention, such a mold that can form the support member having a rounded shape is formed in advance, in accordance with the shape of the support member. Therefore, there is such an advantage that it is unnecessary to introduce a special process in the subsequent member-forming process. In order to form the mold having such a shape, isotropic etching may be performed, or mask patterning or the like, which realizes such a shape, may be used, as described above, for example.  
      Then, in the member-forming process, the projection portion and the support member are formed. Here, they can be formed by using a film formation method (or a film growth method) or the like. Since the mold is formed in advance such that the surface of the support member will be rounded in the mold-forming process, it is possible to produce the above-described first, second, or third recoding/reproducing head of the present invention, relatively easily, without using a special method in the member-forming process.  
      Consequently, according to the production method of the present invention, it is possible to produce the above-described first, second, or third recoding/reproducing head of the present invention efficiently and relatively easily.  
      Incidentally, the production method of the present invention can take various aspects in association with the various aspect of the first, second, or third recording/reproducing head of the present invention.  
      Moreover, if the above-described recording/reproducing head array is produced, the same production method can be used.  
      In one aspect of the production method of the present invention, the mold having the shape corresponding to the rounded shape is formed by performing isotropic etching in the mold-forming process.  
      According to this aspect, by using the properties of the isotropic etching, it is possible to form the mold having the shape corresponding to the rounded shape (i.e. the mold for forming the support member having the rounded shape) relatively easily. Therefore, it is possible to form the surface that is associated with the rounded shape, of the above-described first, second, or third recording/reproducing head, for example. In particular, the first, second, or third recording/reproducing head is produced in size on the order of nanometers, so that it is difficult to realize such a shape by mechanical grinding process or polishing process or the like, and it is also expensive. However, according to this aspect, by effectively use the properties of the isotropic etching, it is possible to realize such a shape easily.  
      In another aspect of the production method of the present invention, the mold having the shape corresponding to the rounded shape is formed by rounding a masking shape of a photoresist in the mold-forming process.  
      According to this aspect, it is possible to reproduce the recording/reproducing head provided with the support member having the rounded shape, as occasion demands, relatively easily, in accordance with the patterning of the photoresist.  
      In another aspect of the production method of the present invention, the mold, having a portion for forming the projection portion, is formed by using a silicon (100) substrate as the mold and by performing anisotropic etching with respect to the silicon substrate, in the mold-forming process.  
      The silicon substrate has such a characteristic that an etching rate differs between the (100) surface and the (111) surface thereof, because of a difference in interatomic bonds in the crystal lattice surfaces of the (100) surface and the (111) surface. Therefore, according to this aspect, it is possible to form the mold in the projective shape (or in a pyramid-shape), which is required for the formation of the projection portion, by performing the anisotropic etching using such a characteristic, in the mold-forming process. Then, the use of the mold allows the formation of the projection portion, relatively easily, in the member-forming process.  
      Incidentally, not only the silicon substrate but also a materials having the above-described characteristic can be used as the mold in place of the silicon substrate.  
      In another aspect of the production method of the present invention, the support member having the rounded shape is formed by ion irradiation, in the member-forming process.  
      According to this aspect, for example, a Focused Ion Beam (FIB) is used to cut, peal off, grind or polish an angular surface, to thereby allow the relatively easy production of the support member having the rounded shape.  
      (Recording Apparatus)  
      The above object of the present invention can be also achieved by a recording apparatus for recording information onto a dielectric recording medium, the recording apparatus provided with: the above-described first, second, or third recording/reproducing head (including its various aspects); and a record signal generating device for generating a record signal corresponding to the information.  
      According to the recording apparatus of the present invention, it is possible to record the data on the basis of the record signal generated by the recording signal generating device, while taking advantage of the above-described first, second, or third recording/reproducing head of the present invention. Namely, it is possible to prevent the rewriting of the data by the generation (the application) of the unexpected electric field or the like, as described above, and prevent the superimposition of noise to the record signal, or the like. As a result, it is possible to appropriately apply the electric field corresponding to the record signal to the dielectric recoding medium. Therefore, there is such a great advantage that it is possible to record the data with more stability.  
      (Reproducing Apparatus)  
      The above object of the present invention can be also achieved by a reproducing apparatus for reproducing information recorded on a dielectric recording medium, the reproducing apparatus provided with: the above-described first, second, or third recording/reproducing head (including its various aspects); an electric field applying device for applying an electric field to the dielectric recording medium; an oscillating device whose oscillation frequency varies depending on a difference in a capacitance corresponding to a non-linear dielectric constant of the dielectric recording medium; and a reproducing device for demodulating and reproducing an oscillation signal from the oscillating device.  
      According to the reproducing apparatus of the present invention, by applying an electric field to the dielectric recording medium by using the electric filed applying device, the oscillation frequency of the oscillating device is changed, due to a change in the capacitance corresponding to a change in the non-linear dielectric constant of the dielectric recording medium. Then, the oscillation signal corresponding to the change in the oscillation frequency of the oscillating device is demodulated and reproduced by the reproducing device, to thereby reproduce the data.  
      Particularly in the present invention, the data can be reproduced by taking advantage of the above-described first, second, or third recording/reproducing head of the present invention. Namely, it is possible to prevent the change in the oscillation frequency by the generation (the application) of the unexpected electric field or the like, as described above, and prevent the superimposition of noise to the oscillation signal, or the like. Therefore, there is such a great advantage that it is possible to reproduce the data with more stability.  
      The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with reference to preferred embodiment of the invention when read in conjunction with the accompanying drawings briefly described below.  
      As explained above, the first recording/reproducing head of the present invention is provided with the support member and the projection portion, and the support member has a rounded shape at the surface thereof on the side facing the dielectric recording medium, in the mounted portion on which the projection portion is mounted. The second recording/reproducing head of the present invention is provided with the support member and the projection portion, and the support member has a relatively rounded shape at the mounted portion on which the projection portion is mounted, as compared to the shape at the other portion on which the projection portion is not mounted. The third recording/reproducing head of the present invention is provided with the support member and the projection portion, and the support member has a rounded shape at the inhibition portion where the generation (the application) of an electric field is to be inhibited, out of the support member. Therefore, it is possible to prevent the concentration of the electric field at the support member, and it is also possible to effectively inhibit or remove the generation (the application) of the unexpected electric field (or the unexpected discharge) from the support member.  
      Moreover, the production method of the present invention is provided with the mold-forming process and the member-forming process. Therefore, it is possible to produce the first, second, or third recording/reproducing head of the present relatively easily and efficiently.  
      Moreover, the recording apparatus of the present invention is provided with the first, second, or third recording/reproducing head of the present invention and the record signal generating device. Therefore, it is possible to receive various benefits owned by the first, second, or third recording/reproducing head of the present invention, and thus, it is possible to record the data with more stability.  
      Furthermore, the reproducing apparatus of the present invention is provided with: the first, second, or third recording/reproducing head; the electric field applying device; the oscillating device; and the reproducing device. Therefore, it is possible to receive various benefits owned by the first, second, or third recording/reproducing head of the present invention, and thus, it is possible to reproduce the data with more stability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  and  FIG. 1B  are cross sectional views, side views, and plan views, conceptually showing one specific example of a recording/reproducing head in an embodiment of the present invention;  
       FIG. 2A  and  FIG. 2B  are cross sectional views, side views, and plan views, conceptually showing another specific example of the recording/reproducing head in the embodiment of the present invention;  
       FIG. 3  is a cross sectional view conceptually showing a size of the recording/reproducing head in the embodiment of the present invention;  
       FIG. 4  is a perspective view conceptually showing one process of a production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 5  is a cross sectional view conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 6A  and  FIG. 6B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 7A  and  FIG. 7B  are a cross sectional view and a plan view, respectively, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 8A  and  FIG. 8B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 9A  and  FIG. 9B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 10A  and  FIG. 10B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 11A  and  FIG. 11B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 12A  and  FIG. 12B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 13A  and  FIG. 13B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 14A  and  FIG. 14B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 15A  and  FIG. 15B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 16A  and  FIG. 16B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 17A  and  FIG. 17B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 18A  and  FIG. 18B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 19A  and  FIG. 19B  are cross sectional view and plan view, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 20A  and  FIG. 20B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 21A  and  FIG. 21B  are cross sectional views, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 22  is a cross sectional view, conceptually showing another process of the production method for the recording/reproducing head in the embodiment of the present invention;  
       FIG. 23A  and  FIG. 23B  are a perspective view and a plan view, respectively, conceptually showing one modification example of the recording/reproducing head in the embodiment of the present invention;  
       FIG. 24A  and  FIG. 24B  are a perspective view and a plan view, respectively, conceptually showing another modification example of the recording/reproducing head in the embodiment of the present invention;  
       FIG. 25A  and  FIG. 25B  are a perspective view and a plan view, respectively, conceptually showing another modification example of the recording/reproducing head in the embodiment of the present invention;  
       FIG. 26  is a block diagram conceptually showing a basic structure of a dielectric recording/reproducing apparatus in an embodiment which adopts the recording/reproducing head in the embodiment of the present invention;  
       FIG. 27A  and  FIG. 27B  are an explanatory diagram and a cross sectional view, respectively, conceptually showing a dielectric recording medium used for information reproduction on the dielectric recording/reproducing apparatus in the embodiment;  
       FIG. 28  is a cross sectional view conceptually showing a record operation of the dielectric recording/reproducing apparatus in the embodiment;  
       FIG. 29  is a cross sectional view conceptually showing a reproduction operation of the dielectric recording/reproducing apparatus in the embodiment; and  
       FIG. 30A  and  FIG. 30B  are cross sectional views conceptually showing one example of a state of discharge from a probe, in the dielectric recording/reproducing apparatuses in the embodiment and in the comparison. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Embodiments of the present invention will be hereinafter explained with reference to the drawings.  
      (1) Embodiment of Recording/Reproducing Head  
      At first, with reference to  FIG. 1  to  FIG. 25 , the embodiment of the recording/reproducing head of the present invention will be explained.  
      (i) Structure of Recording/Reproducing Head  
      At first, with reference to  FIG. 1  to  FIG. 3 , the structure of the recording/reproducing head in the embodiment (i.e. its basic structure) will be explained.  FIG. 1A  and  FIG. 1B  conceptually show one specific example of the structure of the recording/reproducing head in the embodiment.  FIG. 2A  and  FIG. 2B  conceptually show another specific example of the structure of the recording/reproducing head in the embodiment.  FIG. 3  conceptually shows a relationship of the size of the recording/reproducing head in the embodiment.  
      As shown in the view on the lower left of  FIG. 1A , a recording/reproducing head  100  in the embodiment is provided with: a projection portion  110 ; and a support member  130 .  
      The projection portion  110  has a narrowed and pointed tip so that an electric field is applied to a dielectric recoding medium  20  as described later (refer to  FIG. 27 ) from the tip side in the record/reproduction operations of the recording/reproducing head  100 . In particular, the projection portion  110  preferably has electric conductivity, obtained by doping boron or the like to diamond at the time of production. Moreover, not only diamond, but also a material having electric conductivity, such as boron nitride, can be used. However, the projection portion  110  is preferably constructed by using a harder material because it could contact the dielectric recording medium  20 . The tip portion of the projection portion  110  is a significant factor to determine the radius of the polarization formed correspondingly to the record data recorded onto the dielectric recording medium  20  as described later. Thus, out of the tip portion, particularly, the size of a portion which directly contacts the dielectric recording medium  20  is preferably extremely small. For example the radius of the portion which directly contacts the dielectric recording medium  20  is on the order of 10 nm.  
      The support member  130  is a base for supporting the recording/reproducing head  100 . The support member  130  has electric conductivity as with the projection portion  110 . Moreover, as described later, the support member  130  and the projection portion  110  may be formed in one body (refer to  FIG. 4  etc.).  
      Furthermore, as described later, the projection portion  110  and the support member  130  constitute a part of a resonance circuit  14  in the reproduction operation as a part of a probe  11  (refer to  FIG. 26 ). Thus, it is possible to select their materials according to the inductance of the projection portion  110  and the support member  130  so as to obtain a desired resonance frequency (oscillation frequency). Moreover, by selecting the material in this manner, it is also possible to change the vibration frequency of the probe  11 , as occasion demands.  
      Particularly in the embodiment, the end portion (i.e. the tip portion) of the support member  130  is rounded. Namely, as shown in the view on the upper left of  FIG. 1A  (the view in which the recording/reproducing head  100  is observed from the top side, i.e. the side of the support member  130 ), there is not any angular part on the end portion of the support member  130 .  
      In addition, as shown in the view on the lower right of  FIG. 1A  (the cross sectional view of the support member  130 ), there is not any angular part on the cross section of the support member  130 . Namely, the support member  130  has such a shape that there is not any angular part over its entire surface.  
      If the support member  130  has an angular part (e.g. if the support member  130  has a rectangular shape on its cross section), an electric field concentrates at the angular part. In the extreme case, there is a possibility that an unexpected electric field (or discharge) is generated (applied) between the angular part and the dielectric recording medium  20 . This is caused by the characteristic that the electric field can leak to the outside of the conductor at the portion where the electric field concentrates. Such an unexpected electric field or the like is undesirable in a dielectric recording/reproducing apparatus  1  described later (refer to  FIG. 26 ), which uses SNDM, for example, for detecting the polarization condition of the dielectric recording medium  20  by applying an electric field to between the recording/reproducing head  100  and the dielectric recording medium  20  (or a return electrode  12 ).  
      However, in the embodiment, the support member  130  does not have an angular part but has a rounded shape, to thereby give such an advantage that it is possible to prevent the concentration of an electric field at the support member  130 . By this, if an electric field is applied to between the recording/reproducing head  100  and the dielectric recording medium  20 , it is possible to realize an appropriate discharge (i.e. the appropriate application of an electric field) between the projection portion  110  and the dielectric recording medium  20  (or the return electrode  12 ). By preventing the concentration of the electric field at the support member  130 , it is possible to inhibit or remove the application (the generation) of the unexpected electric field or the like between the support member  130  and the dielectric recording medium  20  (or the return electrode  12 ).  
      Moreover, as shown in  FIG. 1B , if not the entire portion of the support member  130  but the angular parts or corners thereof are rounded, the other portion except the angular parts (i.e. the surface portions of the support member  130 ) is not necessarily rounded. Even such a recording/reproducing head  101  can receive the above-described various benefits.  
      As shown in  FIG. 2A , out of the support member  130 , a surface on the side facing the dielectric recording medium  20  may be rounded. Namely, from the viewpoint of preventing the concentration of the electric field and further preventing the application of the unexpected electric field or the like, as described above, it is enough if there is not any angular part in a portion where the unexpected electric field is possibly applied between the support member  130  and the dielectric recording medium  20  (or the return electrode  12 ). In other words, it is enough if the portion where the concentration of the electric field or the generation of the unexpected discharge is to be inhibited may have a rounded shape. Therefore, out of the support member  130 , even if there is an angular part on the side not-facing the dielectric recording medium  20  (i.e. on the side where the projection portion  110  is not formed), it is possible to inhibit or remove the application of the unexpected electric field or the like, which is an obstacle to the record/reproduction operations.  
      It is also possible to prevent an unexpected discharge between the support member  130  and a return electrode  12  described later (refer to  FIG. 26 ). Therefore, it is possible to appropriately form the resonance circuit  14  (refer to  FIG. 26 ), to thereby allow the appropriate reproduction of polarization information recorded in the dielectric recording medium  20 . Preventing the application of an unexpected electric field between the support member  130  and the return electrode  12  increases the degree of freedom in determining the arrangement/position of the return electrode  12  or the like. For example, it is possible to place the return electrode  12  closer to the recording/reproducing head  100 . This has such an advantage that it is possible to further prevent noise, such as floating capacitance, from entering the resonance circuit  14 . Incidentally, the support member  130  in this case is preferably shaped such that there is not an angular part on its surface on the side facing the return electrode  12 .  
      Moreover, even if the projection portion  110  is not formed on one end portion of the support member  130 , the projection portion  110  may be formed at a predetermined position of the support member  130  as shown in  FIG. 2B . Even such a recording/reproducing head  103  can receive the above-described various benefits.  
      Now, the size of the rounded shape of the support member  130  (e.g. the radius of the rounded shape or the like) will be explained with reference to  FIG. 3 , with the radius of the rounded shape as an example.  
      As shown in  FIG. 3 , it is assumed that the distance between the support member  130  and the dielectric recording medium  20  is d. In this case, if the recording/reproducing head  100 , in the condition that the support member  130  is substantially parallel to the recording surface of the dielectric recording medium  20 , contacts the dielectric recording medium  20  to perform the record and reproduction operations, the distance d corresponds to the height of the projection portion  110 . Then, under the assumption that the radius of the rounded shape of the support member  130  is R, it is preferable that R≧d/10.  
      If the support member  130  has the shape rounded enough to satisfy this condition, it is possible to effectively prevent the concentration of the electric field at the support member  130 , and it is possible to inhibit or remove the unexpected discharge from the support member  130  to the dielectric recording medium  20  or the return electrode  12 . As a result, it is possible to appropriately perform the record and reproduction operations by using the recording/reproducing head  100  in the embodiment.  
      Even if the portion having the rounded shape in the recording/reproducing head  100  is a merely smooth surface and the radius thereof cannot be easily evoked or expressed, if the above condition is satisfied in full consideration of the curvature of such a smooth surface, the radius thereof in the case where the smooth surface is regarded as a circular arc, and the like, it is obvious that this aspect is included in the scope of the present invention.  
      It is also conceivable to improve a record speed and a reproduction speed by using a plurality of recording/reproducing heads  100 . In such a case, it is possible to inhibit or remove the application of an unexpected electric field or the like which is possibly applied between the adjacent recording/reproducing heads  100 , or the like, in addition to receiving the above-described various benefits. Therefore, it is possible to remove a noise source, such as crosstalk, which disturbs the information record and reproduction operations, to thereby allow the appropriate record and reproduction of the information. By this, it is possible to increase the degree of freedom in determining the arrangement/position of each of the plurality of recording/reproducing heads  100 . For example, if the recording/reproducing heads  100  can be arranged densely, it is possible to increase a data mount which can be recorded and reproduced per unit time, to thereby improve the record speed and the reproduction speed of the dielectric recording/reproducing apparatus described later.  
      Even if the condition of R≧d/10 is not satisfied, but if the support member  130  has a significantly or properly rounded shape, then, it is possible to significantly prevent the concentration of the electric field at the support member  130 , and it is possible to properly inhibit the application of the unexpected electric field or the like.  
      (ii) Production Method for Recording/Reproducing Head  
      Next, with reference to  FIG. 4  to  FIG. 22 , the production method for the recording/reproducing head in the embodiment will be explained.  FIG. 4  to  FIG. 22  conceptually show each process of the production method for the recording/reproducing head in the embodiment.  
      Incidentally, the recording/reproducing head produced in the production method explained here has the projection portion  110  and the support member  130  which are unified. However, even if the projection portion  110  and the support member  130  are not unified, the recording/reproducing head can be produced in the same production method, and it is obvious that such a production method is also included in the scope of the present invention.  
      At first, as shown in  FIG. 4 , a silicon substrate  201  is prepared. The silicon substrate  201  mainly becomes a mold for the recording/reproducing head. Incidentally, it is preferable to prepare such a silicon substrate  201  that a silicon dioxide film is formed along (or in parallel with) its (100) surface in a crystal lattice structure in a later process. This is, as described later, to form the projective (or pyramid-like) shape of the projection portion  110  by performing anisotropic etching. The silicon substrate  201  is referred to as a (100) substrate.  
      Incidentally, the explanation below goes on with reference to mainly a-a cross sectional views in  FIG. 4 , as well as b-b cross sectional views and plan views viewed from a direction c (i.e. plan views of the silicon substrate  201  viewed from its top side).  
      Then, as shown in  FIG. 5 , silicon dioxide (SiO 2 ) films  202  are formed with respect to a front surface (or an upper surface in  FIG. 5 ) and back surface (or a downside surface in  FIG. 5 ) of the silicon substrate  201 . In this case, the silicon dioxide films  202  may be formed on the surfaces by providing the silicon substrate  201  under an oxidizing atmosphere at high temperature.  
      Then, as shown in  FIG. 6A , a photoresist  203  is coated by spin coating method, for example, and patterning is performed. Specifically, after the photoresist  203  is coated onto the silicon dioxide film  202  formed on one of the surfaces of the silicon substrate  201 , ultraviolet rays or the like are irradiated thereon with a photo mask in which a portion corresponding to the projective portion  110  is patterned. Then, by developing it, the patterning of the photoresist  203  is performed as shown in  FIG. 6A .  
      Incidentally,  FIG. 6B  shows the silicon substrate  201  etc. in  FIG. 6A  viewed from the direction c (i.e. from the side where the photoresist  203  is patterned). As shown in  FIG. 6B , in the portion where the projection portion  110  and the support member  130  of the recording/reproducing head  100  will be formed later, a window (or space portion) at which the photoresist  203  is not coated can be seen. The projection portion  110  and the support member  130  will be formed later in accordance with the shape of this window.  
      Incidentally, as shown in  FIG. 6B , in order to make the support member  130  having such a shape that there is not an angular part on the end portion, the photoresist  203  is patterned by using a photo mask for making the end portion rounded.  
      Then, as shown in  FIG. 7A , etching is performed with respect to the silicon substrate  201  in which the photoresist  203  is patterned as shown in  FIG. 6 . Here, for example, BHF (Buffered HydroFluoric acid) or the like is used to perform the etching with respect to the portion where the photoresist  203  is not coated out of the silicon dioxide film  202 . However, other etchant may be used for the etching, or dry etching may be performed for the etching.  
      After the etching of the silicon dioxide film  202 , the photoresist  203  is removed. Here, the removal of the photoresist  203  may be performed by dry etching or wet etching.  
       FIG. 7B  shows the silicon substrate  201  etc. in  FIG. 7A  viewed from the direction c. As shown in  FIG. 7B , in the portion where the projection portion  110  will be formed later, a window at which the silicon dioxide film  202  is not coated can be seen, and the silicon substrate  201  can be seen at the window.  
      Then, as shown in  FIG. 8A , isotropic etching is performed with respect to the silicon substrate  201 . Here, for example, the isotropic etching is performed by dry etching which uses Xenon Difluoride (XeF 2 ) gas or the like, for example. Other gases may be used for the isotropic etching, or wet etching may be performed for the isotropic etching.  
      As described above, by the isotropic etching, the silicon substrate  201  is etched to be a rounded mold. By using the mold of the silicon substrate  201  etched in this manner, it is possible to produce the recording/reproducing head having the shape as shown in  FIG. 1  and  FIG. 2 .  
      Moreover, in order to realize the rounded shape on the end portion on the top side of the support member  130 , as with the recording/reproducing head  100  shown in  FIG. 1 , a Focused Ion Beam (FIB) is preferably used, for example.  
       FIG. 8B  is a b-b cross sectional view of the silicon substrate  201  shown in  FIG. 8A . As shown in  FIG. 8B , even in the b-b cross sectional view, the silicon substrate  201  is etched to be the rounded mold.  
      Then, as shown in  FIG. 9A , the silicon substrate  201  is again oxidized, to thereby form the silicon dioxide films  202  on its surfaces. Here, as in the explanation in  FIG. 5 , the silicon dioxide films  202  may be formed on the surfaces by providing the silicon substrate  201  under an oxidizing atmosphere at high temperature.  
      Incidentally, out of the silicon substrate  201 , a thickness (t 1 ) of the silicon dioxide film  202  formed on the surface of the portion which is bored by the isotropic etching is thinner than a thickness (t 2 ) of the silicon dioxide film  202  formed in the process in  FIG. 5 . Namely, the silicon substrate  201  is oxidized such that t 1 &lt;t 2  is valid. Therefore, quick oxidization is preferable to the silicon substrate  201  in the process shown in  FIG. 9 .  
      Incidentally,  FIG. 9B  is a b-b cross sectional view of the silicon substrate  201  etc. shown in  FIG. 9A . As shown in  FIG. 9B , the silicon dioxide films  202  are formed on the silicon substrate  201 .  
      Then, as shown in  FIG. 10A , the photoresist  203  is coated again for patterning. At this time, the phtoresist  203  is patterned except the portion where the projection portion  110  will be formed.  
      Incidentally,  FIG. 10B  is a b-b cross sectional view of the silicon substrate  201  etc. shown in  FIG. 10A . As shown in  FIG. 10B , the portion of the silicon substrate  201  which will not be the mold of the projection portion  110  is covered with the photoresist  203 , and the photoresist  203  is not formed in the portion of the silicon substrate  201  which will be the mold of the projection portion  110 .  
      Then, as shown in  FIG. 11A , etching is performed with respect to the silicon dioxide film  202  in accordance with the patterning of the photoresist  203  as shown in  FIG. 10 , and then, the photoresist  203  is removed. The etching here is performed in the same procedure as that in  FIG. 7 .  
      Incidentally,  FIG. 11B  is a b-b cross sectional view of the silicon substrate  201  etc. shown in  FIG. 11A . As shown in  FIG. 11B , the silicon dioxide film  202  in the portion where the projection portion  110  will not be formed is not etched and remains on the silicon substrate  201 . The silicon dioxide film  202  in the portion where the projection portion  110  is formed is etched in accordance with the patterning of the photoresist  203 .  
      Then, as shown in  FIG. 12A , anisotropic etching is performed with respect to the silicon substrate  201 . Here, for example, alkaline etchant, such as TMAH (TetraMethyl Ammonium Hydroxide) and KOH (Potassium Hydroxide), is used for the anisotropic etching. Here, the silicon substrate  201  has such a characteristic that the etching can be performed in the normal direction of the (100) surface (i.e. in a direction perpendicular to the silicon substrate  201  in  FIG. 12A ), but it is relatively difficult to perform the etching in the normal direction of the (111) surface (i.e. a direction having an angular difference of approximately 45 degrees with respect to the silicon substrate  201  in  FIG. 12A ). To perform the anisotropic etching by using this characteristic, the silicon substrate  201  is etched such that it has a shape corresponding to the projective portion  110  shown in  FIG. 1  (i.e. a projection shape or pyramid shape).  
      Incidentally,  FIG. 12B  is a b-b cross sectional view of the silicon substrate  201  etc. shown in  FIG. 12A . The anisotropic etching is performed with respect to the silicon substrate  201 , as shown in  FIG. 12B , so that an etching rate is lower in the outer portion of the window of the silicon dioxide film  202 , and the etching rate is higher in the central portion of the window. As a result, the tip portion of a hole formed by the etching has a sharp pointed shape.  
      Then, as shown in  FIG. 13A , the silicon dioxide film  202  is removed by etching. At this time, the etching is performed such that the silicon dioxide film  202  formed on the surface of the portion which is bored by the isotropic etching out of the silicon substrate  201  is removed, while the silicon dioxide film  202  formed in the process in  FIG. 5  remains.  
      Incidentally,  FIG. 13B  is a b-b cross sectional view of the silicon substrate  201  etc. shown in  FIG. 13A . As shown in  FIG. 13B , the silicon dioxide film  202  formed on the surface of the portion which is bored by the isotropic etching out of the silicon substrate  201  is removed, while the silicon dioxide film  202  formed in the process in  FIG. 5  remains.  
      Then, as shown in  FIG. 14A  and  FIG. 14B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 14A , in methanol containing diamond powders, the surfaces of both the silicon substrate  201  and the silicon dioxide film  202  formed thereon are scratched, by vibrating the diamond powders by using ultrasound or the like, for example. By scratching the surfaces as described above, diamond nuclei can be formed in the following process (refer to  FIG. 15 ).  
      Then, as shown in  FIG. 15A  and  FIG. 15B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 15A , a diamond film is formed by Hot Filament CVD (Chemical Vapor Deposition). For example, using CH 4  (methane) gas as a material, the diamond film is formed on the silicon substrate  201 . In particular, the diamond film grows at the position of the scratch which is made in the process in  FIG. 14 . Incidentally, not only Hot Filament CVD, but also Microwave Plasma CVD or other film growth methods or the like may be used to grow the diamond film.  
      Moreover, the diamond film is used as the above-described projection portion  110 , so that it needs to have electric conductivity. Therefore, B (Boron) is doped in the diamond film by adding a doping gas, such as B 2 H 6  (diborane) and (CH 3 O) 3 B (trimethoxy boron). Other doping gases may be used to add the electric conductivity to diamond.  
      Incidentally, the method of growing the diamond film is not limited to the one by the scratch process as shown in  FIG. 14 . The diamond film may be grown by applying a negative bias voltage to the silicon substrate  201  at the initial stage of the CVD process, or by applying ultra micro diamond powders to the silicon substrate  201 , to thereby use the ultra micro diamond powders as the nuclei for growing the diamond film.  
      Then, as shown in  FIG. 16A  and  FIG. 16B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 16A , diamond particles which are growing on the silicon dioxide film  202  are removed. The removal of an extremely small amount of silicon dioxide film  202  by way of etching with BHF or the like can result in the removal of the diamond particles. By this, it is possible to form the projection portion  110  and the support member  130  which have appropriate shapes.  
      Then, as shown in  FIG. 17A  and  FIG. 17B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 17A , the diamond film is further grown by using Hot Filament CVD or the like, for example, to thereby form the projection portion  110  and the support member  130 .  
      Incidentally, in this case, the support member  130  and the projection portion  110  are formed in one body, so that in the explanation below, the projection portion  110  shall include a function as the support member  130 .  
      Then, after the projection portion  110  is formed, etching is performed, as shown in  FIG. 18A  and  FIG. 18B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 18A , and the silicon dioxide film  202  is removed. Here, for example, BHF or the like is used to remove the silicon dioxide film  202 .  
      Then, as shown in  FIG. 19A , photosensitive polyimide  205  is formed on a surface opposite to the side where the portion corresponding to the projection portion  110  is formed, in the portion corresponding to the support member  130  The photosensitive polyimide  205  is used for attachment to a glass  206  (refer to  FIG. 20 ) for supporting or maintaining the entire recording/reproducing head in a later process.  
      Incidentally,  FIG. 19B  shows the silicon substrate  201  etc. in  FIG. 19A  viewed from the direction c. As shown in  FIG. 19B , the photosensitive polyimide  205  is patterned on a portion opposite to a portion extending in the longitudinal direction out of the portion corresponding to the support member  130  (i.e. on a support base  130   a ). This portion extending in the longitudinal direction corresponds to one specific example of the “mounted portion on which the projection portion is mounted” in the present invention. In addition, from the viewpoint of preventing the application of the unexpected electric field or the like more effectively, even the support base  130   a  may be also treated as one specific example of the “mounted portion on which the projection portion is mounted” in the present invention.  
      Incidentally, with respect to the specific size of the recording/reproducing head shown in  FIG. 19B , the portion extending in the longitudinal direction is preferably 50 μm or less wide. Then, preferably, the portion opposite to the extending in the longitudinal direction is approximately 5 mm×1˜1.5 mm. However, they are not limited to the above size. With respect to the shape thereof, it is not limited to a T-shape as shown in  FIG. 19B , but it may be other shapes such as a L-shape.  
      In this case, the support member  130  is unified with a support base  130   a . The support base  130   a  is fixed, and the support member  130  is unified with the support base  130   a  such that the support member  130  can move (or wobble or oscillate) slightly as a cantilever in accordance with its elasticity. Even in this case, the support member  130  and the support base  130   a  may be collectively referred to as the support member  130 .  
      Then, as shown in  FIG. 20A  and  FIG. 20B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 20A , the glass  206  to which a groove-cutting process is performed is attached to the photosensitive polyimide  205 . The glass  206  is a member for supporting or maintaining the entire recording/reproducing head. By connecting an actuator or the like to the glass  206 , it is possible to displace the recording/reproducing head on or above the dielectric recording medium, in the recording and reproduction operations of the dielectric recording/reproducing apparatus described later.  
      Moreover, the groove-cutting machining is performed to the glass  206 , by forming a cut in the vicinity of the center of the glass  206 . This is formed to easily break the glass  206  in a process described later (refer to  FIG. 22 ).  
      Incidentally, the glass  206  is large enough to cover the whole projection portion  110 . However, the size of the glass  206  shown in  FIG. 20A  and  FIG. 20B  is merely an example. Even if the glass  206  is larger than or smaller than this size, it is enough if it is large enough to support the entire recording/reproducing head.  
      Then, as shown in  FIG. 21A  and  FIG. 21B , which is a b-b cross sectional view of the silicon substrate  201  etc. associated with  FIG. 21A , the silicon substrate  201  is removed. Here, the silicon substrate  201  is removed from the projection portion  110  by using RIE (Reactive Ion Etching). However, other methods may be used to remove the silicon substrate  201 .  
      Then, as shown in  FIG. 22 , the glass  206  is broken along the cut, to thereby complete the recording/reproducing head  100  (or  101 ) which can be used as the probe  11  described later.  
      (iii) Modified Examples of Recording/Reproducing Head  
      Then, with reference to  FIG. 23  and  FIG. 25 , the modified example of the recording/reproducing head in the embodiment will be explained.  FIG. 23  and  FIG. 25  conceptually show structures of the recording/reproducing head in the modified examples.  
      As shown in  FIG. 23A , a recording/reproducing head  104  whose end portion of the support member  130  is rounded may receive the above-described various benefits. Namely, even the recording/reproducing head  104  having such a shape that the angular part of the end portion is removed can inhibit or remove the application of the unexpected electric field or the like.  
      Incidentally,  FIG. 23B  shows the recording/reproducing head  104  from the bottom side. It shows that the end portion is rounded.  
      Moreover, as shown in  FIG. 24A , a recording/reproducing head  105  whose front surface on the side facing the dielectric recording medium  20  is rounded may receive the above-described various benefits. Even such a recording/reproducing head  105  can inhibit or remove the application of the unexpected electric field or the like.  
      Incidentally,  FIG. 24B  is a cross sectional view of the recording/reproducing head  105 . It shows that the front surface of the support member  130  on the side facing the dielectric recording medium  20  is rounded.  
      Moreover, as shown in  FIG. 25A , even in such a recording/reproducing head  106  that portions corresponding to the tip angular parts or tip corners of the support member  130  on the side facing the dielectric recording medium  20  are rounded, it is possible to achieve a significant effect, from the viewpoint of preventing the concentration of the electric field, to thereby inhibit or remove the application of the unexpected electric field, or the like.  
      Incidentally,  FIG. 25B  shows the recording/reproducing head  106  viewed from the bottom side. It shows that the tip angular parts or tip corners of the support member  130  on the side facing the dielectric recording medium  20  are rounded and the upper side portion (i.e. the portion on the side not facing the dielectric recording medium  20 ) has an angular shape.  
      (2) Embodiment of Recording/Reproducing Apparatus  
      Next, the recoding/reproducing apparatus which uses the recording/reproducing head in the embodiment described above will be explained.  
      (i) Basic Structure  
      At first, the basic structure of the dielectric recording/reproducing apparatus in the embodiment will be explained with reference to  FIG. 26 .  FIG. 26  conceptually shows the basic structure of the dielectric recording/reproducing apparatus in the embodiment.  
      The dielectric recording/reproducing apparatus  1  is provided with: the probe  11  for applying an electric field with its tip portion facing a dielectric material  17  of the dielectric recording medium  20 ; the return electrode  12  for returning the high-frequency electric field for reproduction applied from the probe  11 ; an inductor L placed between the probe  11  and the return electrode  12 ; an oscillator  13  which oscillates at a resonance frequency determined from the inductor L and a capacitance Cs in a portion formed in the dielectric material  17  under the probe  11  and polarized correspondingly to the record information; an alternating current (AC) signal generator  21  for applying an alternating electric field which is intended to detect the polarization condition recorded in the dielectric material  17 ; a record signal generator  22  for recording the polarization condition into the dielectric material  17 ; a switch  23  for switching outputs from the AC signal generator  21  and the record signal generator  22 ; a High Pass Filter (HPF)  24 ; a demodulator  30  for demodulating a FM signal modulated by the capacitance Cs corresponding to the polarization condition owned by the dielectric material  17  under the probe  11 ; a signal detector  34  for detecting data from the demodulated signal; and a tracking error detector  35  for detecting a tracking error signal from the demodulated signal.  
      The probe  11  is connected to the oscillator  13  via the HPF  24 , and connected to the AC signal generator  21  and the record signal generator  22  via the HPF  24  and the switch  23 . Incidentally, with respect to the probe  11 , for example, a cantilever shape or a needle shape, as in  FIG. 1  and  FIG. 2 , or the like is known as its specific shape.  
      Particularly in the embodiment, as the probe  11 , the recording/reproducing head  100  in the embodiment described above is used. Namely, the recording/reproducing head in which there is not an angular part on the support member  130  is used as the probe  11 . By using such a recording/reproducing head  100  as the probe  11 , it is possible to prevent the concentration of the electric field at the support member  130  and the application of the unexpected electric field or the like. The advantages will described in detail later (refer to  FIG. 30 ).  
      Incidentally, it is also possible that a plurality of probes  11  are provided. In this case, a plurality of AC signal generators  21  are preferably provided for the respective probes  11 . Moreover, in order to distinguish, on the signal detector (detectors)  34 , reproduction signal corresponding to each of a plurality of the AC signal generators  21 , it is preferable that a plurality of signal detectors  34  are provided and that each of the signal detectors  34  obtains reference signal from the corresponding AC signal generator  21 , to thereby output the corresponding reproduction signal.  
      The return electrode  12  is an electrode for returning the high-frequency electric field applied to the dielectric material  17  from the probe  11  (i.e. a resonance electric field from the oscillator  13 ), and is placed to surround the probe  11 . Incidentally, the shape and placement of the return electrode  12  can be arbitrarily set as long as the high-frequency electric field can return to the return electrode  12 .  
      The inductor L is placed between the probe  11  and the return electrode  12 , and may be formed using a microstripline, for example. The inductor L and the capacitance Cs constitute the resonance circuit  14 . The inductance of the inductor L is determined such that this resonance frequency is approximately 1 GHz, for example.  
      The oscillator  13  is an oscillator which oscillates at the resonance frequency determined from the inductor L and the capacitance Cs. The resonance frequency varies, depending on the change of the capacitance Cs. Therefore, FM modulation is performed correspondingly to the change of the capacitance Cs determined by the polarization domain corresponding to the recorded data. By demodulating this FM modulation signal, it is possible to read the data recorded in the dielectric recording medium  20 .  
      Incidentally, as described in detail later, the probe  11 , the return electrode  12 , the oscillator  13 , the inductor L, the HPF  24 , and the capacitance Cs in the dielectric material  17  constitute the resonance circuit  14 . The FM signal amplified on the oscillator  13  is outputted to the demodulator  30 .  
      The AC signal generator  21  applies an alternating electric field to between the return electrode  12  and an electrode  16 . The frequency of the alternating electric field is approximately 5 kHz, and the alternating electric field is applied to the domain of the dielectric material  17 . In the dielectric recording/reproducing apparatus having the plurality of proves  11 , the frequencies of the alternating electric fields are used as reference signals in the signal detector (detectors)  34  to distinguish reproduction signals detected with the probes  11 .  
      The record signal generator  22  generates a signal for recording (hereinafter referred to as a “record signal”), which is supplied to the probe  11  at the time of recording. This record signal is not limited to a digital signal but may be an analog signal. This record signal includes various signals, such as audio data, video data, and digital data for a computer. An AC signal which is superimposed to the record signal is used, as a reference signal in the reproduction operation, to distinguish and reproduce the reproduction signal of each probe  11 .  
      The switch  23  selects its output to supply an AC signal (the alternating electric field) from the AC signal generator  21  at the time of reproducing, or a record signal from the record signal generator  22  at the time of recording, to the probe  11 . A mechanical relay or a semiconductor circuit may be used for this device. In the case of the analog signal, the relay is preferably provided, and in the case of the digital signal, the semiconductor circuit is preferably provided.  
      The HPF  24  includes an inductor and a condenser. The HPF  24  is used to constitute a high pass filter for cutting off a signal system to prevent the signals obtained from the AC signal generator  21  and the record signal generator  22  from interfering with the oscillation of the oscillator  13 . The cut-off frequency is f=1/{2π{square root}(LC)}, wherein L is the inductance of the inductor included in the HPF  24 , and C is the capacitance of the condenser included in the HPF  24 . The frequency of the AC signal is approximately 5 KHz, and the resonance frequency of the oscillator  13  is approximately 1 GHz, so that the separation at a first LC filter can be performed sufficiently. A higher-order filter may be used, but since the number of elements increases, the size of the apparatus may be increased.  
      The demodulator  30  demodulates the resonance frequency of the oscillator  13 , which is FM-modulated due to the small change of the capacitance Cs, and reconstructs a waveform corresponding to the polarized condition of a portion which is traced by the prove  11 . If the recorded data are digital data of “0” and “1”, there are two types of frequencies which are modulated, and the data is reproduced easily by distinguishing the frequencies.  
      The signal detector  34  reproduces the recorded data from the signal demodulated on the demodulator  30 . A lock-in amplifier is used as the signal detector  34 , for example, and synchronized detection is performed on the basis of the frequency of the alternating electric field of the AC signal generator  21 , to thereby reproduce the data. Incidentally, it is obvious that other phase detection devices may be used.  
      The tracking error detector  35  detects a tracking error signal for controlling the apparatus (especially, tracking operation), from the signal demodulated on the demodulator  30 . The detected tracking error signal is inputted into a tracking mechanism for the control.  
      Next, one example of the dielectric recording medium  20  shown in  FIG. 26  will be explained with reference to  FIG. 27A  and  FIG. 27B .  FIG. 27A  and  FIG. 27B  conceptually show one example of the dielectric recording medium  20  used in the embodiment.  
      As shown in  FIG. 27A , the dielectric recording medium  20  is a disc-shaped dielectric recording medium, and is provided with: a center hole  10 , an inner area  7 , a record area  8 , and an outer area  9 . The inner area  7 , the record area  8 , and the outer area  9  are placed concentrically from the center hole  10  in this order. The center hole  10  is used in the case where the dielectric recording medium  20  is mounted on a spindle motor or the like.  
      The record area  8  is an area to record the data therein and has tracks and spaces between the tracks. Moreover, on the tracks and the spaces, such areas are provided that record therein control information associated with the record and reproduction. Furthermore, the inner area  7  and the outer area  9  are used to recognize the inner position and the outer position of the dielectric recording medium  20 , respectively, and can be used as areas to record therein information about the data which is recorded, such as a title, its address, a recording time length, and a recording capacity. Incidentally, the above-described construction is one example of the dielectric recording medium  20 , and other construction, such as a card-shape, can be also adopted.  
      Moreover, as shown in  FIG. 27B , the dielectric recording medium  20  is formed such that the electrode  16  is laminated on a substrate  15  and that the dielectric material  17  is laminated on the electrode  16 .  
      The substrate  15  is Si (silicon), for example, which is a preferable material in its strength, chemical stability, workability, or the like. The electrode  16  is intended to apply an electric field between the electrode  16  and the probe  11  (or the return electrode  12 ). By applying such an electric field to the dielectric material  17  that is greater than the coercive electric field of the dielectric material  17 , the polarization direction is determined. By determining the polarization direction in accordance with the data, the record operation is performed.  
      The dielectric material  17  is formed by using a known technique, such as spattering method of LiTaO 3  or the like, which is a ferroelectric substance, onto the electrode  16 . The record operation is performed with respect to such a Z surface of LiTaO 3  that the plus and minus surfaces of the polarization have a 180-degree domain relationship. It is obvious that other dielectric materials may be used. The dielectric material  17  forms the small polarization at high speed by using a direct current bias voltage and a voltage for the data which are both applied at the same time.  
      Alternatively, as the shape of the dielectric recoding medium  20 , for example, there are a disc shape and a card shape and the like. The displacement of the relative position with the probe  11  is performed by the rotation of the dielectric recording medium  20 , or by displacing linearly either the probe  11  or the dielectric recording medium  20 .  
      (ii) Operation Principle  
      Next, with reference to  FIG. 28  and  FIG. 30 , the operation principle of the dielectric recording/reproducing apparatus  1  in the embodiment will be explained. Incidentally, in the explanation below, a part of the constituent elements of the dielectric recoding/reproducing apparatus  1  shown in  FIG. 26  is extracted and explained.  
      (Record Operation)  
      At first, with reference to  FIG. 28 , the record operation of the dielectric recording/reproducing apparatus  1  in the embodiment will be explained.  FIG. 28  conceptually shows the record operation of recording the information.  
      As shown in  FIG. 28 , by applying an electric field which is greater than the coercive electric field of the dielectric material  17  to between the probe  11  and the electrode  16 , the dielectric material  17  is polarized having directions corresponding to the direction of the applied electric field. Then, by controlling an applied voltage (an applied electric field) to change the polarization direction, it is possible to record predetermined information. This uses such a characteristic that the polarization direction is reversed when an electric field greater than the coercive electric field of a dielectric substance (particularly, a ferroelectric substance) is applied to the dielectric substance and that the polarization direction is maintained after stopping applying the electric field.  
      For example, it is assumed that the domains have a downward polarization P when an electric field is applied from the probe  11  to the electrode  16 , and that the domains have an upward polarization P when an electric field is applied from the electrode  16  to the probe  11 . This corresponds to a condition where the information is recorded. If the probe  11  is moved in a direction shown with the arrow, a detection voltage is outputted as a rectangular wave having a high level or a low level (i.e. the digital signal), correspondingly to the polarization P. Incidentally, this level varies depending on the extent of the polarization P, to thereby allow the recording as the analog signal.  
      (Reproduction Operation)  
      Next, with reference to  FIG. 29 , the reproduction operation of the dielectric recording/reproducing apparatus  1  in the embodiment will be explained.  FIG. 29  conceptually shows the reproduction operation of reproducing the information.  
      The non-linear dielectric constant of a dielectric substance changes correspondingly to the polarization direction of the dielectric substance. The non-linear dielectric constant of the dielectric substance can be detected as a difference in the capacitance of the dielectric substance or a difference in the change of the capacitance, when an electric field is applied to the dielectric substance. Therefore, by applying an electric field to a dielectric material and detecting, at that time, a difference in the capacitance Cs or a difference in the change of the capacitance Cs in a certain domain of the dielectric material, it is possible to read and reproduce the data recorded as the polarization direction of the dielectric material.  
      Specifically, at first, as shown in  FIG. 29 , an alternating electric field from the not-illustrated AC signal generator  21  is applied to between the electrode  16  and the probe  11 . The alternating electric field has such an electric field strength that is not beyond the coercive electric field of the dielectric material  17 , and has a frequency of approximately 5 kHz, for example. The alternating electric field is generated mainly to distinguish the difference in the change of the capacitance corresponding to the polarization direction of the dielectric material  17 . Incidentally, in place of the alternating electric field, a direct current bias voltage may be applied to form an electric field in the dielectric material  17 . The application of the alternating electric field causes the generation of an electric field in the dielectric material  17  of the dielectric recording medium  20 .  
      Then, the probe  11  is approached to the recording surface until the distance between the tip of the probe  11  and the recording surface becomes extremely small on the order of nanometers. Under this condition, the oscillator  13  is driven. Incidentally, in order to detect the capacitance Cs of the dielectric material  17  under the probe  11  highly accurately, it is preferable to contact the probe  11  with the surface of the dielectric material  17 , i.e. the recording surface. However, in order to read the data recorded in the dielectric material  17  at high speed, it is necessary to relatively displace the probe  11  on the dielectric recording medium  20  at high speed. Thus, in view of reliability in the high-speed displacement, and the prevention of damage caused by the collision and friction between the probe  11  and the dielectric recording medium  20 , or the like, it is practically better to make the probe  11  approach the recording surface close enough to regard this as the actual contact (substantially contact), than make the probe  11  contact the recording surface. Then, the oscillator  13  oscillates at the resonance frequency of the resonance circuit, which includes the inductor L and the capacitance Cs associated with the dielectric material  17  under the probe  11  as the constituent factors. The central frequency of the resonance frequency is set to approximately 1 GHz, as described above.  
      Here, the return electrode  12  and the probe  11  constitute a part of the resonance circuit  14  including the oscillator  13 . The high-frequency signal of approximately 1 GHz, which is applied to the dielectric material  17  from the probe  11 , passes through the dielectric material  17  and returns to the return electrode  12 , as shown with solid lines in  FIG. 29 . By placing the return electrode  12  in the vicinity of the probe  11  and shortening a feedback route to the resonance circuit  14  including the oscillator  13 , it is possible to reduce a chance of noise (e.g. floating capacitance) entering the resonance circuit  14 .  
      In addition, the change of the capacitance Cs corresponding to the non-linear dielectric constant of the dielectric material  17  is extremely small, and in order to detect this change, it is necessary to adopt a detection method having high detection accuracy. In a detection method using FM modulation, generally, it is possible to achieve the high detection accuracy, but it is necessary to further improve the detection accuracy to likely detect the small capacitance change corresponding to the non-linear dielectric constant of the dielectric material  17 . Thus, in the dielectric recording/reproducing apparatus  1  in the embodiment (i.e. a recording/reproducing apparatus which uses the SNDM principle), the return electrode  12  is placed in the vicinity of the probe  11  to shorten the feedback route (the feedback path) to the resonance circuit  14  as much as possible. By this, it is possible to obtain extremely high detection accuracy, and thus it is possible to detect the small capacitance change corresponding to the non-linear dielectric constant of the dielectric substance.  
      After the oscillator  13  is driven, the probe  11  is displaced in parallel with the recording surface on the dielectric recording medium  20 . By the displacement, the domain of the dielectric material  17  under the probe  11  is changed, and whenever its polarization direction changes, the capacitance Cs changes. If the capacitance Cs changes, the resonance frequency (the oscillation frequency) of the oscillator  13  changes. As a result, the oscillator  13  outputs a signal which is FM-modulated on the basis of the change of the capacitance Cs.  
      This FM signal is frequency-voltage converted by the demodulator  30 . As a result, the change of the capacitance Cs is converted to the change of a voltage. The change of the capacitance Cs corresponds to the non-linear dielectric constant of the dielectric material  17 . The non-linear dielectric constant corresponds to the polarization direction of the dielectric material  17 . The polarization direction corresponds to the data recorded in the dielectric material  17 . Therefore, a signal obtained from the demodulator  30  is a signal whose voltage changes correspondingly to the data recorded in the dielectric recording medium  20 . Moreover, the signal obtained from the demodulator  30  is supplied to the signal detector  34 , and the data recorded in the dielectric recording medium  20  is extracted by the synchronized detection, for example.  
      At this time, in the signal detector  34 , the AC signal generated by the AC signal generator  21  is used as a reference signal. This makes it possible to extract the data highly accurately by referring the reference signal (i.e. synchronizing with the reference signal), as described above, even if the signal obtained from the demodulator  30  includes much noise or the data to be extracted is weak, for example.  
      Particularly in the embodiment, the recording/reproducing head  100  is used as the probe  11  to perform the above-described record and reproduction operations. Therefore, as described above, it is possible to prevent the concentration of the electric field from occurring at the support member  130 . By this, as shown in  FIG. 30A , it is possible to inhibit or remove the application of the unexpected electric field (i.e. a leakage of the electric field) or the like from the support member  130  to the return electrode  12  and the dielectric recording medium  20 . Therefore, it is possible to appropriately apply a high-frequency electric field and an alternating electric field upon the reproduction, and a pulse electric field upon the recording, from the probe  11  to the dielectric recording medium  20 .  
      If, as shown in  FIG. 30B , the probe having the angular support member  130   a  is used to perform the above-described record and reproduction operations, there is a possibility that the concentration of the electric field occurs, especially at the angular parts or corners of the support member  130   a . The concentration of the electric field causes the leakage of the electric field to the outside of the support member  130   a . The leakage of the electric field (the unexpected electric field) could be likely applied between the support member  130   a  and the return electrode  12  or the dielectric recording medium  20 . Such application of the unexpected electric field may cause the resonance of the resonance circuit  14  to be disturbed or may cause the application of a stable alternating electric field to be prevented.  
      However, in the embodiment, it is possible to effectively prevent the concentration of the electric field at the support member  130 , the application of the unexpected discharge, or the like, so that it is possible to stabilize the record and reproduction operations, and it is possible to increase reliability as the dielectric recording/reproducing apparatus  1 .  
      Moreover, in the construction such as a multi-probe having a plurality of recording/reproducing heads, it is possible to inhibit or remove the application of unexpected electric fields or the like from the support member  130  in one recording/reproducing head to the projection portions  110  and the support members  130  in the adjacent recording/reproducing heads, in addition to receiving the above-described various benefits. Therefore, it is possible to effectively prevent the application of noise, such as crosstalk, to thereby stabilize the appropriate record and reproduction of the information.  
      Furthermore, in the above embodiment, the dielectric material  17  is used as a recording layer, but from the viewpoint of the presence or absence of spontaneous polarization and the non-linear dielectric constant, the dielectric material  17  is preferably a ferroelectric substance.  
      The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.  
      The entire disclosure of Japanese Patent Application No. 2003-392779 filed on Nov. 21, 2003 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.