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able roughness characteristic and reduction of residue defects and to provide an actinic-ray- or radiation-sensitive resin film therefrom and a method of forming a pattern using the com› position. 

[0064] The single FIGURE is a section view schematically showing the definition of taper angle mentioned in Examples. 

## DETAILED DESCRIPTION OF THE INVENTION 

[0065] The present invention will be described below. 

[0066] Note that, with respect to the expression of a group ( or an atomic group) used in this specification, the expression without explicitly referring to whether the group is substi› tuted or unsubstituted encompasses not only groups with no substituents but also groups having one or more substituents. For example, the expression "alkyl group" encompasses not only alkyl groups having no substituents (viz. unsubstituted alkyl groups) but also alkyl groups having one or more sub› stituents (viz. substituted alkyl groups). 

[0067] In the present invention, the terms "actinic rays" and "radiation" mean, for example, a mercury lamp bright line spectrum, far ultraviolet rays represented by an excimer laser, extreme ultraviolet rays, X-rays, electron beams and the like. In the present invention, the term "light" means actinic rays or radiation. The expression "exposure" used herein, unless oth› erwise noted, means not only light irradiation using a mercury lamp, far ultraviolet, X-rays, EUV light, etc. but also lithog› raphy using particle beams, such as an electron beam and an ion beam. 

[0068] The actinic-ray- or radiation-sensitive resin compo› sition of the present invention comprises [1] a resin that when acted on by an acid, increases its solubility in an alkali devel› oper (hereinafter also referred to as an acid-decomposable resin or resin (P)), [2] a compound that when exposed to actinic rays or radiation, generates an acid (hereinafter also referred to as an acid generator or compound (Q)), and [3] a basic compound (R) with a structure to be specified below. 

[0069] The inventors have found that high sensitivity, favorable pattern shape, favorable roughness characteristic and reduction of residue defects can be attained by employing a composition comprising a basic compound (R) with a speci› fied structure. Further, the inventors have found that this effect is especially striking when a pattern is formed on an acid substrate. 

[0070] The above-mentioned components of the composi› tion will be sequentially described below. 

[0071] [1] Acid-decomposable resin The composition of the present invention contains an acid-decomposable resin (P). 

[0072] <Repeating Unit (A)> 

[0073] The acid-decomposable resin comprises an acid› decomposable repeating unit (A). The repeating unit (A) is a repeating unit that when acted on by an acid, is decomposed to thereby generate an alkali-soluble group. 

[0074] As the alkali-soluble group, there can be mentioned a phenolic hydroxyl group, a carboxyl group, a fluoroalcohol group, a sulfonic acid group, a sulfonamido group, a sulfo› nylimido group, an (alkylsulfonyl)(alkylcarbonyl)methylene group, an (alkylsulfonyl)(alkylcarbonyl)imido group, a bis (alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imido group, a bis(alkylsulfonyl)methylene group, a bis(alkylsulfo- 

## BRIEF DESCRIPTION OF DRAWINGS 

nyl)imido group, a tris(alkylcarbonyl)methylene group, a tris (alkylsulfonyl)methylene group or the like. 

[0075] As preferred alkali-soluble groups, there can be mentioned a phenolic hydroxyl group, a carboxyl group, a fluoroalcohol group (preferably hexafluoroisopropanol) and a sulfonic acid group. 

[0076] The acid-decomposable group is preferably a group as obtained by substituting the hydrogen atom of any of these alkali-soluble groups with an acid-cleavable group. 

[0077] As the acid eliminable group, there can be men› tioned, for example, -C(R$_{36}$)(R$_{37}$)(R$_{38}$ ), -C(R 36 ) (R 37 ) (OR$_{39}$), ----C(R$_{01}$)(R$_{02}$)(OR$_{39}$) or the like. 

[0078] In the formulae, each of R$_{36 }$to R$_{39 }$independently represents an alkyl group, a cycroalkyl group, a monovalent aromatic ring group, a combination of an alkylene group and a monovalent aromatic ring group or an alkenyl group. R$_{36 }$ and R$_{37 }$may be bonded with each other to thereby form a ring structure. 

[0079] Each of R$_{01 }$ to R$_{02 }$ independently represents a hydrogen atom, an alkyl group, a cycroalkyl group, a monovalent aromatic ring group, a combination of an alky› lene group and a monovalent aromatic ring group or an alk› enyl group. 

[0080] Preferably, the acid-decomposable group is a cumyl ester group, an enol ester group, an acetal ester group, a tertiary alkyl ester group or the like. A tertiary alkyl ester group is more preferred. 

[0081] The repeating unit (A) is preferably any of those of general formula (V) below. 

[0082] In general formula (V), 

[0083] each of Rs 1, Rs$_{2 }$ and Rs$_{3 }$ independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, a halogen atom, a cyano group or an alkoxycarbonyl group, provided that Rs$_{2 }$ may be bonded to Ls to thereby form a ring, which Rs$_{2 }$ represents an alkylene group. 

[0084] Ls represents a single bond or a bivalent connecting group, provided that when a ring is formed in cooperation with Rs$_{2}$ , Ls represents a trivalent connecting group. 

[0085] Rs$_{4 }$ represents an alkyl group, and each ofRss and Rs$_{6 }$ independently represents a hydrogen atom, an alkyl group, a cycloalkyl group or a monovalent aromatic ring group, provided that Rss and Rs $_{6 }$may be bonded to each other to thereby form a ring, and provided that Rss and Rs$_{6 }$ are not simultaneously hydrogen atoms. 

[0086] General formula (V) will be described in greater detail below. 

[0087] As a preferred alkyl group represented by each of Rs$_{1 }$ to Rs$_{3 }$ in general formula (V), there can be mentioned an optionally substituted alkyl group having up to 20 carbon atoms, such as a methy 1 group, an ethy 1 group, a propy 1 group, an isopropyl group, an n-butyl group, a sec-butyl group, a 

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