100  US 7,858,289  B2  99  7.  The positive resist composition for electron beam, X-ray  or EUV as claimed in claim  5,  wherein the resin capable of  decomposing by the action of an acid to increase the solubility  in an alkali developer has a repeating unit represented by  formula (V):  4.  A pattern forming method comprising:  5.  The positive resist composition for electron beam, X-ray  or EUV as claimed in claim  3,  wherein the resin capable of  decomposing by the action of an acid to increase the solubility  in an alkali developer has a hydroxystyrene repeating unit.  6.  The positive resist composition for electron beam, X-ray  or EUV as claimed in claim  5,  wherein the resin capable of  decomposing by the action of an acid to increase the solubility  in an alkali developer has a repeating unit represented by  formula (II) and a repeating unit represented by formula (III):  wherein,  each R$_{01 }$ independently represents a hydrogen atom, an  alkyl group, a cycloalkyl group, a halogen atom, a cyano  group or an alkoxycarbonyl group;  each of L$_{1 }$ and L$_{2}$ ,  which may be the same or different,  represents a hydrogen atom, an alkyl group, a cycloalkyl  group or an aralkyl group;  M represents a single bond or a divalent linking group;  Q represents an alkyl group, a cycloalkyl group or an  alicyclic or aromatic ring group which may contain a  heteroatom;  A represents a halogen atom, a cyano group, an acyl group,  an alkyl group, an alkoxy group, an acyloxy group or an  alkoxycarbonyl group;  at least two members out of Q, Mand L$_{1 }$ may combine to 65  form a 5- or 6-membered ring; and  each of m and n represents an integer of Oto 4.  12.  The positive resist composition for electron beam,  X-ray or EUV as claimed in claim  1,  wherein the compound  having a proton acceptor functional group and capable of  producing an acid radical upon irradiation with an actinic ray  or radiation to reduce or lose the acceptor property or to  change the proton acceptor functional group to be acidic is a  compound represented by formula (A3):  11.  The positive resist composition for electron beam,  X-ray or EUV as claimed in claim  2,  wherein the partial  structure of the proton acceptor functional group is selected  from the group consisting of crown ether, aza-crown ether,  tertiary amine, secondary amine, primary amine, pyridine,  imidazole and pyrazine structures.  10.  The positive resist composition for electron beam,  X-ray or EUV as claimed in claim  1,  wherein the partial  structure of the proton acceptor functional group is selected  from the group consisting of crown ether, aza-crown ether,  tertiary amine, secondary amine, primary amine, pyridine,  imidazole and pyrazine structures.  9.  The positive resist composition for electron beam, X-ray  or EUV as claimed in claim  3,  wherein a weight average  molecular weight of the resin capable of decomposing by the  action of an acid to increase the solubility in an alkali devel› oper is 5,000 or less.  8.  The positive resist composition for electron beam, X-ray  or EUV as claimed in claim  7,  wherein X$_{1 }$represents an acid  decomposable group.  wherein,  each of Ra, Rb, and Re independently represents a hydro› gen atom, a fluorine atom, a chlorine atom, a cyano  group or an alkyl group; and  X$_{1 }$ represents a hydrogen atom or an organic group.  3.  The positive resist composition for electron beam, X-ray  or EUV as claimed in claim  1,  further comprising:  a resin capable of decomposing by the action of an acid to 10  increase the solubility in an alkali developer.  Rx represents a hydrogen atom or a monovalent organic  group,  R  represents a monovalent organic group containing a  proton acceptor functional group, or a monovalent  organic group containing an ammonium group, and  when Bis -N(Rx)-, Rand Rx may combine to form a  ring.  forming a resist film from the positive resist composition  claimed in claim  1,  exposing said resist film with an electron beam, X-ray or 15  EUV, and  developing said resist film.  (A3)  RIO  x- (V)  Ra  Re  I  I  ---t C -C  -t- 1  I  Rb  C02-X1  (III)  (II) 