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2008/0081281, etc., oligomers such as calixarene and resin structures as described below in detail. 

<Resin (P)> 

The resin (P) contained in the radiation-sensitive compo› sition, in particular the positive working resist composition is a resin having a repeating unit (A) having an ionic structural site and capable of decomposing upon irradiation with an actinic ray or radiation to generate an acid; and a repeating unit (B) having at least one phenolic hydroxyl group, a part or all of hydrogen atoms of the hydroxyl group or groups each being protected by a group capable ofleaving by the action of an acid, wherein the ionic structural site of the repeating unit (A) is a structure capable of generating an acid anion in a side chain of the resin (P) upon irradiation with an actinic ray or radiation. 

(1) Repeating Unit (A): 

As the repeating unit (A), any repeating unit is useful so far as it is a repeating unit having an ionic structural site and capable of decomposing upon irradiation with an actinic ray or radiation to generate acid, wherein the ionic structural site is a structure capable of generating an acid anion in a side chain of the resin upon irradiation with an actinic ray or radiation. 

As the repeating unit (A), for example, repeating units represented by any one of the following general formulae (III) to (V) are preferable. 

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In the foregoing general formulae (III) to (V), each ofR$_{04}$, Ros and R$_{07 }$to R$_{09 }$independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, a halogen atom, a cyano group or an alkoxycarbonyl group; 

each ofX$_{1 }$to X$_{3 }$independently represents a single bond, an arylene group, an alkylene group, a cycloalkylene group, -0-, -SO$_{2}$ -, -CO-, -N(R$_{33}$)-or a divalent linking group composed of a combination thereof; 

R$_{2}$s represents an alkyl group, a cycloalkyl group, an alk› enyl group, an aryl group or an aralkyl group; 

each ofR$_{26}$ , R $_{27 }$and R$_{33 }$independently represents a hydro› gen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group or an aralkyl group; and 

A represents an ionic structural site capable of decompos› ing upon irradiation with an actinic ray or radiation to gener› ate an acid anion in a side chain of the resin. 

In the foregoing general formulae (III) to (V), examples of the alkyl group represented by R$_{04 }$to Ros and R$_{07 }$ to R$_{09 }$ which is preferable include an optionally substituted alkyl group having not more than 20 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a hexyl group, a 2-ethylhexyl group, an octyl group and a dodecyl group. Of these, an alkyl groups having not more than 8 carbon atoms is more preferable. 

Examples of the cycloalkyl group include a cycloalkyl group which may be of a monocyclic type or a polycyclic type. Of these, an optionally substituted cycloalkyl group of a monocyclic type having from 3 to 8 carbon atoms, for example, a cyclopropyl group, a cyclopentyl group and a cyclohexyl group, is preferable. 

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Of these, a fluorine atom is more preferable. 

As the alkyl group contained in the alkoxycarbonyl group, the same alkyl groups as those in the foregoing R$_{04 }$to R$_{0}$s and R$_{07 }$to R$_{09 }$are preferable. 

Examples of the alkyl group represented by R$_{2}$s to R$_{27 }$and R$_{33 }$ which is preferable include an optionally substituted alkyl group having not more than 20 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a hexyl group, a 2-ethylhexyl group, an octyl group and a dodecyl group. Of these, an alkyl groups having not more than 8 carbon atoms is more preferable. 

Examples of the cycloalkyl group include a cycloalkyl group which may be of a monocyclic type or a polycyclic type. Of these, an optionally substituted cycloalkyl group of a monocyclic type having from 3 to 8 carbon atoms, for example, a cyclopropyl group, a cyclopentyl group and a cyclohexyl group, is preferable. 

Examples of the alkenyl group which is preferable include an optionally substituted alkenyl group having from 2 to 6 carbon atoms, for example, a vinyl group, a propenyl group, an ally! group, a butenyl group, a pentenyl group, a hexenyl group and a cyclohexenyl group. 

Examples of the aryl group which is preferable include an optionally monocyclic or polycyclic aromatic group having from 6 to 14 carbon atoms. Specific examples thereofinclude a phenyl group, a tolyl group, a chlorophenyl group, a meth› oxypheny I group and a naphthy I group. Also, ary I groups may be bonded to each other to form a multi-ring. 

Examples of the aralkyl group include an optionally sub› stituted aralkyl group having from 7 to 15 carbon atoms, for example, a benzyl group, a phenethyl group and a cumyl group. 

As the ring formed through bonding ofR$_{26 }$and R$_{27 }$to each other together with a nitrogen atom, those of forming a 5-membered to 8-membered ring are preferable. Specific examples thereof include pyrrolidine, piperidine and pipera› zme. 

As the arylene group represented by X$_{1 }$ to X$_{3}$ , optionally substituted arylene groups having from 6 to 14 carbon atoms are preferable. Specific examples thereof include a phenylene group, a tolylene group and a naphthylene group. 

Examples of the alkylene group which is preferable include an alkylene group having from 1 to 8 carbon atoms, for example, a methylene group, an ethylene group, a propy› lene group, a butylene group, a hexylene group and an octy› lene group. 

