preferred embodiments according to the present invention will be described below with reference to the drawings . fig1 is a sectional view schematically showing the structure of a multi - charged beam lens according to the first embodiment of the present invention . a multi - charged beam lens 100 has a structure in which three electrode substrates 110 a , 110 b , and 110 c are arranged via insulators ( spacers ) 160 . the three electrode substrates 110 a , 110 b , and 10 c have lens apertures 130 a , 130 b , and 130 c , voltage application portions ( electrode portions ) 140 a , 140 b , and 140 c , which control a trajectory of charged beams passing through the lens apertures 130 a , 130 b , and 130 c , insulating portions 150 a , 150 b , and 150 c , and assembly grooves 120 a , 120 b , and 120 c . the insulators 160 are interposed between the grooves 120 a , 120 b , and 120 c , positioning the three electrode substrates 110 a , 110 b , and 10 c . the electrode substrates 110 a to 110 c may be made of a conductor or semiconductor . use of silicon as the material for the electrode substrates 110 a to 110 c makes it possible to perform reactive ion etching or wet etching using a strong alkali and to facilitate the processing . the grooves 120 a to 120 c do not always extend through the substrates , and their surfaces may partially be recessed . the voltage application portions 140 a to 140 c can be formed by various methods such as cvd and sputtering and can be formed with ease . it is preferable to use a noble metal as the material for the voltage application portions 140 a to 140 c . this is because the noble metal resists oxidation and can last for a long time . the insulating portions 150 a to 150 c are formed on the surfaces of the electrode substrates 110 a to 110 c . it is preferable to use silicon dioxide as the material for the insulating portions 150 a to 150 c . this is because the silicon dioxide can easily be formed on the surfaces of the electrode substrates 110 a to 110 c by various film formation means such as cvd and sputtering . the shape of each insulator 160 is not limited to any specific one . to easily assemble the multi - charged beam lens while positioning it at high precision , the shape is preferably cylindrical . in this embodiment , out of the voltage application portion 140 a of the upper electrode substrate , the voltage application portion 140 b of the intermediate electrode substrate , and the voltage application portion 140 c of the lower electrode substrate , the upper electrode substrate voltage application portion 140 a and the lower substrate voltage application portion 140 c receive the same potential and are typically grounded . at this time , portions ( in this case , the edge portions of the grooves 120 a , 120 b , and 120 c ) where the electrode substrates are in contact with the insulators 160 between the electrode substrates and the voltage application portions 140 a , 140 b , and 140 c , serving as electrodes , are separated from each other via the insulating portions 150 a , 150 b , and 150 c formed on the surfaces of the electrode substrates . accordingly , surface discharge , which may occur on the surface of each insulator 160 , can be reduced . as shown in fig1 , the voltage application portion 140 b of the intermediate electrode substrate typically receives a negative potential with respect to the potential of the voltage application portion 140 a of the upper electrode substrate and the voltage application portion 140 c of the lower electrode substrate . however , the voltage application portion 140 b may receive a positive potential . in this embodiment , the multi - charged beam lens 100 comprises three electrode substrates . however , the number of electrode substrates is not limited to three and can arbitrarily be set . an example of a method of fabricating the electrode substrates 110 a , 110 b , and 110 c shown in fig1 will be described with reference to fig2 a to 2h . in the step shown in fig2 a , a silicon wafer 201 is prepared , and a resist is applied to the surface of the silicon wafer 201 by spin coating or the like . after that , the wafer is patterned in the exposure and developing steps , forming a mask 202 . in the step shown in fig2 b , lens apertures 230 and an assembly groove 220 are formed by dry etching ( anisotropic etching ) using etching gas such as sf 6 gas . thereafter , the mask 202 is removed in the step shown in fig2 c . in the step shown in fig2 d , an insulating layer 250 of silicon dioxide is formed on the surface of the silicon wafer 201 by thermal oxidation . in the step shown in fig2 e , a conductive material is sputtered to at least the inner wall of each lens aperture 230 of the silicon wafer 201 and its periphery , and preferably the entire surface ( including the inner wall of the lens aperture 230 ) of the silicon wafer 201 , forming a conductive film 203 . as the conductive material for the conductive film 203 , a metal is preferably used . a noble metal which resists oxidation is more preferable , and gold is most preferable . in the step shown in fig2 f , resist is applied to the upper and lower surfaces of the silicon wafer by spin coating or the like . after that , the resist is patterned in the exposure and developing steps , forming a mask 204 . in the step shown in fig2 g , the conductive film 203 is etched by reactive ion etching using chlorine , argon , or the like . thereafter , in the step shown in fig2 h , the mask 204 is removed . an electrode substrate 110 , which has the voltage application portion 140 , lens apertures 130 , assembly grooves 120 , and insulating portion 150 , is obtained . the insulator 160 ( fig1 ) is arranged in the assembly groove 120 of the electrode substrate 110 obtained in the above - mentioned steps . another electrode substrate 110 is stacked thereon . in this manner , the multi - charged beam lens 100 shown in fig1 can be obtained . if the multi - charged beam lens is constituted by four or more electrode substrates as well , the multi - charged beam lens can be fabricated using the same method as described above . in the schematic sectional view shown in fig1 , four electron lenses each comprising the four lens apertures 130 a , 130 b , or 130 c are illustrated . electron lenses can be arranged in accordance with a one - or two - dimensional design specification . in a typical multi - charged beam lens , several hundred or several thousand electron lenses can be two - dimensionally arranged . an electron beam exposure apparatus ( drawing apparatus ) using a multi - charged beam lens , which can be manufactured by the above - mentioned method , will be described . the following example will describe an exposure apparatus which adopts an electron beam as a charged beam . the present invention can also be applied to an exposure apparatus using another type of beam , such as an ion beam , as a charged beam . fig3 a and 3b are views schematically showing the main part of an electron beam exposure apparatus using a multi - charged beam lens which can be manufactured by the present invention . in fig3 a , reference numeral 1 denotes multi - source modules each of which forms a plurality of electron images and emits electron beams from the electron images . as shown in fig3 b , 3 × 3 multi - source modules 1 are arrayed . the multi - source module 1 will be described later in detail . as shown in fig3 a , reference numerals 21 , 22 , 23 and 24 denote magnetic lens arrays . in each magnetic lens array , magnetic disks md each have 3 × 3 openings having the same shape and are vertically arranged with a spacing between them . the magnetic lens arrays are excited by common coils cc . as a consequence , each aperture functions as the magnetic pole of one of magnetic field lenses ml , and a lens magnetic field is generated . a plurality of electron source images of each multi - source module 1 are projected onto a wafer 4 by four magnetic lenses ( ml 1 , ml 2 , ml 3 , and ml 4 ) corresponding to the magnetic lens arrays 21 , 22 , 23 , and 24 , respectively . an optical system which acts on electron beams emitted from one multi - source module before the wafer is irradiated with the electron beams is defined as a column hereinafter . that is , in this embodiment , the optical system of the electron beam exposure apparatus has nine columns ( col . 1 to col . 9 ), as shown in fig3 b . an image is once formed by the two corresponding magnetic lenses of the magnetic lens arrays 21 and 22 , and then projected onto the wafer 4 by the two corresponding magnetic lenses of the magnetic lens arrays 23 and 24 . by individually controlling the excitation conditions of the magnetic lens arrays 21 , 22 , 23 , and 24 by the common coils , the optical characteristics ( focal position , image rotation , and magnification ) of each column can be adjusted to be substantially uniform ( i . e ., by the same amount ). reference numeral 3 denotes main deflectors . the main deflectors 3 deflect a plurality of electron beams from the corresponding multi - source module 1 to displace a plurality of electron source images in the x and y directions on the wafer 4 . reference numeral 5 denotes a stage which can move the wafer 4 placed thereon in the x and y directions perpendicular to an optical axis ax ( z - axis ) and in the rotation direction about the z - axis . a stage reference plate 6 is fixed on the stage 5 . reference numeral 7 denotes reflected electron detectors . the reflected electron detectors 7 detect reflected electrons generated when a mark on the stage reference plate 6 is irradiated with an electron beam . fig4 is a view showing a detailed structure of one of the columns . the multi - source module 1 and a function of adjusting the optical characteristics of an electron beam , which comes incident from the multi - source module 1 to the wafer 4 , will be described with reference to fig4 . reference numeral 101 denotes an electron source ( crossover image ) formed by an electron gun . an electron beam emitted from the electron source 101 becomes an almost parallel electron beam via a condenser lens 102 . the condenser lens 102 of this embodiment is an electrostatic lens having three opening electrodes . reference numeral 103 denotes an aperture array having a plurality of openings two - dimensionally arrayed ; 104 , a lens array in which electrostatic lenses having the same optical power are two - dimensionally arrayed ; 105 and 106 , deflector arrays each formed by two - dimensionally arraying electrostatic eight - pole deflectors that can individually be driven ; and 107 , a blanker array formed by two - dimensionally arraying electrostatic blankers that are drivable individually . the multi - charged beam lens 100 according to the preferred embodiment of the present invention constitutes the lens array 104 . the functions will be described with reference to fig5 . the almost parallel electron beam from the condenser lens 102 ( fig4 ) is divided into a plurality of electron beams by the aperture array 103 . each obtained electron beam forms an electron source intermediate image on a corresponding blanker of the blanker array 107 via a corresponding electrostatic lens of the lens array 104 . in this state , the deflector arrays 105 and 106 individually adjust the positions ( in the plane perpendicular to the optical axis ) of the electron source intermediate images formed on the blanker array 107 . an electron beam deflected by each blanker of the blanker array 107 is shielded by a blanking aperture ap in fig4 , so the wafer 4 is not irradiated with the electron beam . on the other hand , an electron beam which is not deflected by the blanker array 107 is not shielded by the blanking aperture ap , so the wafer 4 is irradiated with the electron beam . referring back to fig4 , the plurality of intermediate images of the electron sources formed in each multi - source module 1 are projected onto the wafer 4 via two corresponding magnetic lenses of the magnetic lens arrays 21 and 22 . of the optical characteristics of each column when the plurality of intermediate images are projected onto the wafer 4 , image rotation and magnification factor can be adjusted by the deflector arrays 105 and 106 which can adjust each intermediate image position on the blanker array . the focal position of each column can be adjusted by dynamic focus lenses ( electrostatic or magnetic lenses ) 108 and 109 arranged for each column . fig6 shows the system arrangement of this embodiment . in fig6 , a blanker array control circuit 41 individually controls the plurality of blankers that constitute the blanker array 107 . a deflector arrays control circuit 42 individually controls the plurality of deflectors that constituted the deflector arrays 105 and 106 . a d_focus control circuit 43 individually controls the dynamic focus lenses 108 and 109 . a main deflector control circuit 44 controls the main deflector 3 . a reflected electron detection circuit 45 processes a signal from the reflected electron detector 7 . the blanker array control circuits 41 , deflector array control circuits 42 , d_focus control circuits 43 , main deflector control circuits 44 , and reflected electron detection circuits 45 are arranged equal in number to the column ( col . 1 to col . 9 ). a magnetic lens array control circuit 46 controls the common coils of the magnetic lens arrays 21 , 22 , 23 and 24 . a stage drive control circuit 47 drive - controls the stage 5 in cooperation with a laser interferometer ( not shown ) which detects the position of the stage 5 . a main control system 48 controls the plurality of control circuits and manages the entire electron beam exposure apparatus . this embodiment provides a concrete example in which a semiconductor portion coated with an insulating layer is in contact with an insulator . fig7 is a sectional view schematically showing the structure of a multi - charged beam lens according to the second embodiment of the present invention . a multi - charged beam lens 700 has a structure in which three electrode substrates 701 a , 701 b , and 701 c are arranged via insulators 780 . the three electrode substrates 710 a , 710 b , and 710 c have lens apertures 730 a , 730 b , and 730 c , voltage application portions 740 a , 740 b , and 740 c , insulating portions 750 a , 750 b , and 750 , assembly grooves 720 a , 720 b , and 720 c , semiconductor portions 760 a , 760 b , and 760 c , and insulating layers 770 a , 770 b , and 770 c . the insulators 780 are interposed between the grooves 720 a , 720 b , and 720 c , positioning the three electrode substrates 710 a , 710 b , and 710 c . as the material for the electrode substrates 710 a to 710 c , an soi substrate is typically used . the grooves 720 a to 720 c do not always extend through the substrates , and their surfaces may partially be recessed . the voltage application portions 740 a to 740 c can be formed by various methods such as cvd and sputtering and can be formed with ease . it is preferable to use a noble metal as the material for the voltage application portions 740 a to 740 c . this is because the noble metal resists oxidation and can last for a long time . the insulating portions 750 a to 750 c can be formed as buried insulating films for the electrode substrates 710 a to 710 c . the shape of each insulator 760 is not limited to any specific one . to easily assemble the multi - charged beam lens while positioning it at high precision , the shape is preferably cylindrical . in this embodiment , out of the voltage application portion 740 a of the upper electrode substrate , the voltage application portion 740 b of the intermediate electrode substrate , and the voltage application portion 740 c of the lower electrode substrate , the upper electrode substrate voltage application portion 740 a and the lower electrodes substrate voltage application portion 740 c receive the same potential and are typically grounded . at this time , portions ( in this case , the edge portions of the grooves 720 a , 720 b , and 720 c ) where the electrode substrates are in contact with the insulators 780 between the electrode substrates and the voltage application portions 740 a , 740 b , and 740 c serving as electrodes are separated from each other via the insulating portions 750 a , 750 b , and 750 c , semiconductor portions 760 a , 760 b , and 760 c , and insulating layers 770 a , 770 b , and 770 c . accordingly surface discharge , which may occur on the surface of each insulator 80 , can be reduced . as shown in fig7 , the voltage application portion 740 b of the intermediate electrode substrate typically receives a negative potential with respect to the potential of the voltage application portion 740 a of the upper electrode substrate and the voltage application portion 740 c of the lower electrode substrate . however , the voltage application portion 740 b may receive a positive potential . in this embodiment , the multi - charged beam lens 700 comprises three electrode substrates . however , the number of electrode substrates is not limited to three and can arbitrarily be set . an example of a method of fabricating the electrode substrates 710 a , 701 b , and 701 c shown in fig7 will be described with reference to fig8 a to 8h . in the step shown in fig8 a , an soi wafer 800 including silicon wafers 801 and 803 , and a silicon dioxide layer 802 is prepared . in the step shown in fig8 b , a resist is applied by spin coating or the like . after that , the resist is patterned in the exposure and developing steps , forming a mask 804 . in the step shown in fig8 c , lens apertures 830 and an assembly groove 821 are formed in the silicon layer 801 by dry etching ( anisotropic etching ) using etching gas such as sf 6 gas . thereafter , the mask 804 is removed . in the step shown in fig8 d , a resist is applied to the lower side of the silicon layer 803 by spin coating or the like . in the exposure and developing steps , the resist is patterned while being aligned with the pattern on the upper side , forming a mask 805 . in the step shown in fig8 e , an assembly groove 822 is formed in the silicon layer 803 by dry etching ( anisotropic etching ) using etching gas such as sf 6 gas . the mask 805 is removed . thereafter , in the step shown in fig8 f , exposed portions of the silicon dioxide layer 802 are removed by wet etching using hydrofluoric acid or the like , and the silicon surface is oxidized by thermal oxidation . with this operation , an insulating layer 870 , which covers a semiconductor portion 860 , is formed . in the step shown in fig8 g , a resist is applied by spin coating or the like . the resist is patterned in the exposure and developing steps , forming a sacrificial layer 806 . after that , a conductive material is sputtered onto the upper and lower surfaces , forming a conductive film 807 . as the conductive material for the conductive film , a metal is preferably used . a noble metal which resists oxidation is more preferable , and gold is most preferable . in the step shown in fig8 h , ultrasonic cleaning is performed in an organic solvent to remove the sacrificial layer 806 and conductive film 807 thereon . a voltage application portion 740 is formed , and an electrode substrate 710 can be obtained . the insulator 780 ( fig7 ) is arranged in an assembly groove 720 of the electrode substrate 710 obtained in the above - mentioned steps . another electrode substrate 710 is stacked thereon . in this manner , the multi - charged beam lens 700 shown in fig7 can be obtained . if the multi - charged beam lens is constituted by three or more electrode substrates as well , the multi - charged beam lens can be fabricated by using the same method as described above . in the schematic sectional view shown in fig7 , four electron lenses each comprising the four lens apertures 730 a , 730 b , or 730 c are illustrated . electron lenses can be arranged in accordance with a one - or two - dimensional design specification . in a typical multi - charged beam lens , several hundred or several thousand electron lenses can be two - dimensionally arranged . in this embodiment , the thickness of the voltage application portions 740 a , 740 b , and 740 c can be reduced while keeping their structural strength to some extent . since the aspect ratio of the apertures 730 a , 730 b , and 730 c can be reduced , a multi - charged beam lens , which is easier to manufacture , can obtained . the multi - charged beam lens described can also be applied to a charged beam exposure apparatus such as an electron beam exposure apparatus illustrated in fig3 a and 3b . a charged beam exposure apparatus of this type is preferably used to manufacture a device such as a semiconductor device . according to the above - mentioned embodiments , voltage application portions and portions of electrode substrates that are in contact with insulators interposed between the electrode substrates are separated from each other via insulating portions . the triple point of the boundary between each insulator , vacuum region , and electrode is reduced or eliminated . surface discharge which may occur on the surface of each insulator can be reduced without any back electrode arrangement . according to the above - mentioned embodiments , there can be provided a multi - charged beam lens with a high breakdown voltage , high performance , and high reliability . use of the multi - charged beam lens in a charged beam exposure apparatus makes it possible to provide a reliable exposure apparatus . an application example of a device manufacturing method using the above - mentioned electron beam exposure apparatus will be described next . fig9 shows the manufacturing flow of a microdevice ( e . g ., a semiconductor chip such as an ic or lsi , a liquid crystal panel , a ccd , a thin - film magnetic head , a micromachine , or the like ). in step 1 ( circuit design ), a semiconductor device circuit is designed . in step 2 ( eb data conversion ), the exposure control data for an exposure apparatus is created on the basis of the designed circuit pattern . in step 3 ( wafer manufacture ), a wafer is manufactured by using a material such as silicon . in step 4 ( wafer process ), called a preprocess , an actual circuit is formed on the wafer by lithography using the wafer and the exposure apparatus into which the prepared exposure control data is input . step 5 ( assembly ), called a post - process , is the step of forming a semiconductor chip by using the wafer formed in step 4 , and includes an assembly process ( dicing and bonding ) and a packaging process ( chip encapsulation ). in step 6 ( inspection ), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 . after these steps , the semiconductor device is completed and shipped ( step 7 ). fig1 shows the detailed flow of the above - mentioned wafer process . in step 11 ( oxidation ), the wafer surface is oxidized . in step 12 ( cvd ), an insulating film is formed on the wafer surface . in step 13 ( electrode formation ), an electrode is formed on the wafer by vapor deposition . in step 14 ( ion implantation ), ions are implanted in the wafer . in step 15 ( resist processing ), a photosensitive agent is applied to the wafer . in step 16 ( exposure ), the circuit pattern is transferred onto the wafer using the above - mentioned exposure apparatus . in step 17 ( development ), the exposed wafer is developed . in step 18 ( etching ), the resist is etched except for the developed resist image . in step 19 ( resist removal ), an unnecessary resist after etching is removed . these steps are repeated to form multiple circuit patterns on the wafer . the manufacturing method of the application example makes it possible to manufacture , at low cost , a highly - integrated microdevice which has conventionally been hard to manufacture . as many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof , it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims .