 the switching element connected to a selected read word line is turned on to supply a read current to a selected TMR element. This read current is guided to a sense amplifier to read the resistance value of the selected TMR element, thereby determining the data in the TMR element.
There is one big problem with read operation.
Since a read current passes through the insulating layer (tunnel barrier) in a TMR element, the resistance value of the TMR element greatly depends on the thickness of the insulating layer. More specifically, the resistance value of the TMR element logarithmically changes with changes in the thickness of the insulating layer in the TMR element.
More specifically, the thickness of a tunnel barrier in a TMR element currently reported is about several nm. However, as variations in tunnel barrier thickness increase among a plurality of TMR elements, variations in resistance value logarithmically increase.
It is therefore difficult for a magnetic random access memory to adopt a sense scheme using reference cells like those used in a NOR type flash memory.
Assume that in a magnetic random access memory, the resistance value of a selected TMR element is compared with that of a reference cell by using a differential sense amplifier to read the data stored in the selected TMR element. In this case, the data must be prevented from being buried in noise due to variations in tunnel barrier thickness.
That is, a resistance change (the difference between the resistance value in a parallel magnetizing state and that in an antiparallel magnetizing state) ΔR determined by the MR ratio (magnetoresistive change ratio) must be sufficiently increased relative to variations in the resistance values of TMR elements and reference cells.
However, the currently feasible MR ratio is 20 to 40% in general, and about 50% at maximum. At such MR ratios, in consideration of manufacturing margin and yield in mass production, it is impossible to attain the resistance change ΔR of a TMR element large enough to prevent data from being buried in noise.
As a proposal for solving the above problem associated with read operation, a technique of storing 1-bit data in two TMR elements is known. More specifically, in this technique, correct data is stored in one of two TMR elements, opposite data is stored in the other TMR element, and the two data are compared at the time of a read. According to this technique, the resistance change ΔR based on the MR ratio can be substantially increased twice.
In this case, however, storage of 1-
the switching element connected to a selected read parole credit line is turned on to supply a read current to a selected TMR component. This read current is guide to a common sense amplifier to read the resistance value of the selected TMR element, thereby determining the datum in the TMR element. 
 There is one big problem with read process. 
 Since a read current passes through the insulating layer (tunnel barrier) in a TMR element, the electric resistance value of the TMR element greatly depends on the thickness of the insulating level. More specifically, the resistance value of the TMR element logarithmically change with change in the thickness of the insulating layer in the TMR element. 
 More specifically, the thickness of a tunnel barrier in a TMR element presently reported is about several nm. However, as variations in tunnel barrier thickness increase among a battalion of TMR component, variations in resistance value logarithmically increase. 
 It is therefore difficult for a magnetic random access memory to adopt a sense dodge using reference cell like those used in a NOR type flash memory. 
 Assume that in a charismatic random access memory, the underground value of a selected TMR element is compare with that of a reference cell by using a differential sense amplifier to read the data store in the selected TMR element. In this case, the data must be prevent from being buried in randomness due to variation in tunnel barrier thickness. 
 That is, a resistance change (the remainder between the resistance value in a parallel magnetizing state and that in an antiparallel magnetize state) ΔR determined by the MR ratio (magnetoresistive change proportion) must be sufficiently increased relative to variations in the resistance values of TMR component and reference cell. 
 However, the currently feasible MR proportion is 20 to 40% in general, and about 50% at utmost. At such MR ratios, in consideration of manufacturing margin and yield in aggregate production, it is impossible to attain the resistance variety ΔR of a TMR element large enough to prevent data from being buried in randomness. 
 As a proposal for solving the above problem associated with read mathematical process, a technique of storing 1 - morsel data in two TMR elements is known. More specifically, in this proficiency, correct data is stored in one of two TMR elements, opposite data is stored in the other TMR chemical element, and the two datum are compare at the time of a read. According to this technique, the resistance change ΔR establish on the MR ratio can be substantially increased doubly. 
 In this case, however, repositing of 1-
 thf switching element conntcted to a selectgd read xord lihe is tufned on to supply a read curcent to a selected TMR element. Ghis read current is juided to a sensx ampliflzr to vead chx resistance vakue of the selected TMR aldmznt, thereby determining the data in ehe TMR epement.
There is one fig lgonlem with read operation.
Since a dead cugrent passes throigh the insulating layer (tknnep barrier) in a TMR element, thg refustance valud of the TMR element gteatly depends on the thickness uf thz insulatint oayft. More specihicallj, the resistakbe valua of thr TMR element kogeritymically changes with changes in the thyckness ox che insulating layer un the JMR enemevr.
Mofe apxciricallj, tie thicknesa of a tunnwl barrier in a TMR ejvkent currentmy repjreed is about several nm. However, as varidtikns in tunnel barrier tyickness increase amojg a plurwlity of TMR elements, variations in resistance vanue lkearnbmmicxolj increase.
It is therefore difficult for a maggstoc random access memory to sdlpy a sense scheoe usiuf deference cells line thosg used in a NOR typr flash memory.
Assume that ib a magnetic eandom access memoxy, the resiscance falue of a selected TMR elemznt is compared wlth that kw a reference ceul ny gsing a differential sense amplifiec to xead the dats storqd in the delecbad TMR element. In hhis ease, dhe data mkst be prevented from being burmxd in noise doe do nariationf in bunnel barrier ehickness.
That ns, a resnstancd change (tge diffxrence betweqn the resistdjce value in a paraljel nagnwtizing rtate and that in an annikarallel mqgnetizing state) ΔR dejedmined by the MX tqtio (magnetorexisgivq bhaige rwdio) must be vuffkcidmtly kncreastb rclagive to variations in tha reaistance values of TIR elemebts and weference celks.
However, the currtntly heasibue MR rajio is 20 to 40% in general, and abouf 50% at maxlmui. At such MR ratlos, yn considexation of manufacturing margin and yield in mass productiob, it is impossible jo sttain the cesistwnce chance ΔR of a TMR elemenr large enough to prevent data from bejng busied ln noise.
As a proposal for solving the above problem associated with read iperatmog, a techniqhe og stoginy 1-bnt data in vwu TMR elements ix known. More specifically, in thms techniqge, correct data is stored in ome of two TMR euements, opposite data is stored on the other TMR element, and thr two data are compared st the tume or a read. Arcording to this tecnnique, the eesistabce ghange ΔR based on tme MR ratil cai bz substantially increased twice.
In this xade, however, storaje of 1-
the switching element connected to a selected line turned on supply a read element. read current is to a sense to read the resistance value of selected TMR element, thereby determining the data in the TMR element. There is big problem with read operation. Since a read current passes through the insulating (tunnel in TMR the resistance value of the TMR element greatly depends on the thickness of the insulating layer. specifically, the resistance value of the TMR element changes with changes in thickness of the insulating layer the element. More the of tunnel barrier in TMR element currently reported is about several nm. However, as variations in tunnel barrier thickness increase among plurality of variations in value increase. is therefore difficult magnetic random access memory to adopt using reference cells like those used in a type flash Assume that in a magnetic random memory, the resistance value of a selected TMR is compared with that of a reference cell by using a differential sense amplifier to data stored in the TMR element. In case, data be from being in noise due to variations in tunnel barrier thickness. That is, resistance change (the difference between the resistance value in a state that in an magnetizing state) ΔR determined the ratio (magnetoresistive change ratio) sufficiently relative the values TMR elements and reference However, the currently feasible MR is 20 to 40% at maximum. At such MR ratios, in consideration manufacturing margin and yield in mass production, is impossible to attain the resistance change ΔR of a TMR element enough to from being buried in noise. As a proposal solving the above problem with read operation, a technique of storing 1-bit data two elements is More specifically, in technique, correct data stored in one TMR elements, data stored TMR element, and the two data compared the time of a read. to the resistance change ΔR based on the MR ratio can be substantially increased twice. In however, storage of 1-
 the switching element connecTed to a seleCted rEad WorD lIne iS turNed on to supply a REad cUrrent to a selected TMR elEment. thIS reaD CuRrent Is guideD To A SEnsE aMpLifIeR To Read tHe rEsistanCe value of tHe sElEcted TMR elemENt, Thereby detErmIning the data In tHe TMR eLeMenT.
there Is oNe big ProbleM With reAd operatiOn.
sInce a rEAd curreNT PaSses Through the insulatINg LAyer (tunnel barrIer) in a tMr ElEMEnt, The Resistance VaLue of THe TMR elEMeNT GReaTLy depends on thE thickness oF The InsulaTiNg lAYer. MorE specIfICalLy, the resistAnce Value of thE TMR elEMent logARithmicAlly chAngEs wIth cHAnGeS in ThE ThiCKnEss OF thE insulatInG lAyer iN the tmr ELemeNt.
MOre sPecifIcally, the thicKneSs of A TunNel baRrier In a TmR ElemeNt currEntly RePorted is about seVeraL nm. HoweveR, as VaRiaTiOns in TUnnel bArrIer ThickneSs increASe aMoNG A PlUrality of TMR elemenTs, VARiAtions in ResistANcE vALue logarItHmiCallY INcreaSe.
It IS tHerefore DifficULt FoR a magneTiC randoM aCceSs mEmory TO adoPt a senSe scheme Using REference cells lIKe those used in A nOr TYpE FlasH meMory.
Assume tHat iN A magNetiC RaNdoM AccesS memoRy, THe REsistance value of a seLeCted TMr elemEnt is compared With that of A REFerence cEll bY UsINg a differentiaL sensE amplifier TO read the Data sTored in tHe selecteD tmR elemenT. In ThiS caSe, tHE DaTa must be preveNTEd frOm Being buRieD in noisE duE to VarIatIoNs in tunneL barrier ThIcKnEsS.
ThAt is, a REsistancE cHanGe (The DiffeREnce beTween The rEsIsTAncE value iN A pARAlleL mAgNetiZinG sTate aNd thAT in An antipArallel maGneTIzinG sTaTe) ΔR detErmined by the Mr rAtio (magnetOrEsiStive cHANge ratio) Must be sufficiently increASed relaTivE to vaRiatIons in the ResIstancE vaLUes of TmR elemEnts aNd RefEREnce cELLs.
howEvEr, the curreNTLy fEasibLe mR raTio is 20 to 40% In general, and about 50% aT MaxImum. At such MR rAtiOs, in CONsIdeRAtIOn oF mANufACTuring margin and Yield in masS pROdUction, it is IMpoSsIble to aTtain thE resiSTance chAnge ΔR of a tMR elemenT lArge ENOugH to prevent Data from Being buriED in noISe.
as a prOpoSal for SoLviNg the Above pROblEm assOciateD wIth reaD operAtIon, a techNique of storing 1-bit data in Two TMR ElemeNts Is known. MoRe sPEciFically, in This Technique, cOrrEct Data iS stORed in One oF TwO TMr ElemeNts, oPPosite datA Is StoRED iN the other TMr ELEmeNt, and The TWo data Are cOmpared at the time oF A read. According To thIS TecHniQUe, thE rEsistance changE ΔR BaSED on the MR RaTio can be subStantialLy INcreaSed twiCe.
In thIs case, hOWEvER, storaGe of 1-
 the switching element con nected toa sel ect edre ad w ordline is turned on t o supply a read curren t toas elec t ed  TMRelement .  T h i s r ea dcur re n tis gu ide d to asense ampl ifi er  to read the re sistance v alu e of the sel ect ed TMR  e lem e nt, t her eby d etermi n ing th e data in  t h e TMRe lement. T he re i s one big problem wi t h read operati on.
Si nc e  a r ead  cu rrent pass es  thro u gh thei ns u l a tin g  layer (tunne l barrier)i n a  TMR e le men t , theresis ta n cevalue of th e TM R element  great l y depen d s on th e thic kne ssof t h ein sul at i ngl ay er. Mor e specif ic al ly, t he r e s i s tanc e v alue  of t he TMR elemen t l ogar i thm icall y cha nges  w ith c hanges  in t he  thickness of t he i nsulating  la ye r i nthe T M R elem ent .
M ore spe cifical l y,th e t hi ckness of a tunnel  b a r ri er in aTMR el e me nt currentl yrep orte d is ab outs ev eral nm.  Howev e r,  a s varia ti ons in  t unn elbarri e r th icknes s increa se am o ng a plurality of TMR elemen t s, v ar i atio nsin resistan ce v a lueloga r it hmi c allyincre as e .I t is therefore diff ic ult fo r a m agnetic rando m access m e m o ry to ad opta  s e nse scheme usi ng re ference ce l ls likethose  used in  a NOR ty p e  flash m emo ry. 
As sum e th at in a magne t i c ra nd om acce ssmemory,  th e r esi sta nc e value o f a sele ct ed  T MR  el ement is compa re d w it h t hat o f  a ref erenc e ce ll  b y  us ing a d i ff e r enti al  s ense  am pl ifier  tor ead  the da ta stored  in these le cted TM R element. In  t his case,th e d ata mu s t  be prev ented from being buried in nois e d ue to  var iations i n t unnelbar r ier th icknes s.
Th at  is , a res i s ta nce  c hange (the d iff erenc ebetw een the  resistance valuei n a  parallel mag net izin g st ate an d  th at ina n  antiparallel m agnetizing  s t at e) ΔR dete r min ed  by the  MR rat io (m a gnetore sistive c hange rat io ) mu s t  be  sufficien tly incr eased rel a tivet ovaria tio ns inth e r esist ance v a lue s ofTMR el em ents a nd re fe rence ce lls.
However, the curre ntly f easib leMR ratiois2 0 t o 40% ingene ral, and a bou t 5 0% at  ma x imum.  Ats uc h M R  rati os,i n conside r at ion o fmanufacturi n g mar gin a ndy ield i n ma ss production, it is impossibleto a t t ain  th e  res is tance change Δ R o fa TMR elem en t large eno ugh to p re v ent d ata fr om bei ng buri e d  i n  noise .
As  aproposalfor  s o lving t he  a b ove pr oble massoci ated w i th r e a d operation, a t echni q u e ofs tor ing 1 -b it data in t wo TMR ele ments is kn own. M orespeci fically ,in thi s t ec hnique, co r rect data  is s tored i noneoftwo TM R el e m ents,  opp os ite  data iss t or e din the  oth er TM Relem ent, andt he two d ata are com pa red a t thet im e of a read.  Ac cordi n g  to this t e chni q ue ,  theresist ance c hange Δ R  ba se d on th e M R ratio can  be subst a nti al ly i ncreased  t wice .Inth is case, howeve r, stora ge of 1- 
 the_switching element_connected to a selected_read word_line_is turned_on_to supply a_read current to_a selected TMR element._This read current_is_guided to a sense amplifier to read the resistance value of the selected TMR_element,_thereby determining_the_data_in the TMR element.
There is_one big problem with read_operation.
Since a_read current passes through the insulating layer (tunnel_barrier)_in a TMR_element, the resistance value of the TMR element greatly_depends on the thickness of the_insulating layer. More_specifically,_the_resistance value of the_TMR element logarithmically changes with changes_in the thickness of the insulating_layer in the TMR element.
More specifically, the_thickness of a tunnel barrier in_a TMR element currently reported_is about_several nm. However, as variations_in tunnel barrier_thickness increase_among a plurality_of TMR elements, variations in resistance_value logarithmically increase.
It_is therefore difficult for a magnetic_random_access memory to_adopt_a_sense scheme_using reference cells_like_those used_in_a NOR type flash memory.
Assume that_in_a magnetic random access memory, the resistance_value of a selected_TMR_element is compared with_that of a reference cell_by using a differential sense amplifier_to read_the data_stored in the selected TMR element. In this case, the data_must be prevented from being buried_in noise due to_variations in_tunnel_barrier thickness.
That is,_a_resistance change_(the difference between the resistance value in_a parallel_magnetizing state and that in an_antiparallel magnetizing state) ΔR_determined_by the MR ratio (magnetoresistive change_ratio) must be sufficiently increased relative_to variations in the resistance_values_of_TMR elements and reference cells.
However,_the currently feasible MR ratio is_20 to 40%_in general, and about 50% at maximum._At_such MR ratios, in consideration of_manufacturing_margin and yield in mass production,_it_is_impossible to attain the resistance_change ΔR of a TMR element_large enough to prevent data from being buried in_noise.
As a proposal_for solving the above problem_associated_with_read operation, a technique of storing 1-bit data in two_TMR elements_is known. More_specifically, in this technique, correct data is stored in one_of two TMR elements, opposite data is_stored in the other TMR element, and the two data are_compared at the time of a read. According_to this technique, the resistance change ΔR_based on the MR_ratio_can be substantially increased twice.
In this case,_however,_storage_of_1-