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side chains (hereinafter referred to as "component (Cl)") and main chain-degradable resin components (hereinafter referred to as "component (C2)"). 

Examples of the component (Cl) include resins containing at least one structural unit among the aforementioned struc- tural units (all) to (a13), and optionally containing an afore› mentioned structural unit (a2) to (a6) or the like. More spe› cific examples of the component (Cl) include resins containing the structural units ( a 12) and ( a3 2), resins contain› ing the structural units (a12), (a32) and(a5), resins containing the structural units (a13) and (a33), resins containing the structural units (a13), (a33) and (a6), resins containing the structural units ( a 11) and ( a2 ), resins containing the structural units (all), (a2) and (a31), resins containing the structural units (al 1), (a2), (a31) and (a4), resins containing the struc› tural units (all) and (a32), resins containing the structural units (all), (a32) and (a5), resins containing the structural units (all) and (a33), and resins containing the structural units (all), (a33) and (a6). 

Examples of the component (C2) include polymers in which n arm portions each composed of a polymer chain are bonded to an organic group having a valency of n (wherein n represents an integer of 2 or greater) via linking groups that include a joining group which can be cleaved under the action of acid. 

This expression that the joining group "can be cleaved under the action of acid" means that the action of the acid generated from the structural unit (a0) or an optional compo› nent (B) upon exposure can cause the bonding within the main chain of the component (C2) to break at the position of the joining group. 

In these types of polymers, when acid is generated from the structural unit (a0) or an optional component (B) upon expo› sure, the action of the acid causes cleavage of the joining group. As a result, the molecular weight decreases signifi› cantly, and a polar group is formed at the position of the joining group, resulting in an increase in the solubility within an alkali developing solution and a decrease in the solubility within an organic developing solution. 

More specific examples of the component (C2) include polymers having a core portion represented by a general formula (1) shown below and arm portions composed of polymer chains bonded to the core portion (hereinafter referred to as the "polymer (C21)"). 

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In formula ( 1 ), P represents an organic group having a valency of a, a represents an integer of 2 to 20, X 21 represents an arylene group or an alkylene group of 1 to 12 carbon atoms, and X$^{22 }$represents a joining group that can be cleaved under the action of acid. (Core Portion) 

The core portion of the polymer ( C21) is represented by the general formula (1) shown above. 

In the general formula (1 ), a represents an integerof2 to 20, preferably an integer of 2 to 15, and more preferably an integer of3 to 10. Provided a satisfies this range, the resolu› tion improves and an excellent pattern shape can be obtained. 

P represents an organic group having a valency of a. In other words, when Pis divalent (a=2), the core portion of the polymer (C21) is a structure in which two groups represented by are bonded to P. When Pis trivalent (a=3), three groups represented by-X$^{22}$-X 21 - are bonded to P. In this man› ner, as the valency a of P increases, the number of groups -X 22 -X 21 - bonded to P increases, and the polymer (C21) becomes a more dense radial-shaped structure. 

The organic group for P preferably contains 1 to 20 carbon atoms, more preferably 2 to 15 carbon atoms, and still more preferably 3 to 12 carbon atoms. 

Examples of the organic group include aliphatic hydrocar› bon groups and aromatic hydrocarbon groups. 

The aliphatic hydrocarbon group may be a chain-like group, a cyclic group, or a combination thereof, and may be either saturated or unsaturated. 

Examples of the aromatic hydrocarbon group include hydrocarbon groups containing an aromatic hydrocarbon ring, and the group may be composed solely of the aromatic hydrocarbon ring, or may be a combination of the aromatic hydrocarbon ring and an aliphatic hydrocarbon group. 

The organic group may also include a linking group such as an ether group, polyether group, ester group [----C(=O)› O-], carbonyl group [-C(=O)-], -NH-, -N=, -NH-C(=O)- or -NR 25 (wherein R 25 represents an alkyl group), or a silicon atom within the group structure. 

Examples of the alkyl group for R$^{25 }$include lower alkyl groups of 1 to 5 carbon atoms. 

Further, a part or all of the hydrogen atoms within the organic group may or may not each be substituted with a substituent such as an alkyl group, alkoxy group, halogen atom or hydroxyl group. 

As the alkyl group with which a hydrogen atom of the organic group may be substituted, an alkyl group of 1 to 5 carbon atoms is preferred, and a methyl group, ethyl group, propyl group, n-butyl group ortert-butyl group is particularly desirable. 

As the alkoxy group with which a hydrogen atom of the organic group may be substituted, an alkoxy group of 1 to 5 carbon atoms is preferred, a methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group ortert› butoxy group is more preferred, and a methoxy group or ethoxy group is particularly desirable. 

Examples of the halogen atom with which a hydrogen atom of the organic group may be substituted include a fluorine atom, chlorine atom, bromine atom and iodine atom, and a fluorine atom is particularly desirable. 

Specific examples of the organic group for P include groups having the structures represented by formulas shown below. 

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