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virtue of the above combination of the structural units, EL margin and resist pattern shape can be improved. 

In the present invention, as the component (Al’), a copoly› mer represented by general formula (Al ’-11) shown below which includes three types of structural units is particularly desirable. 

[Chemical Formula 58] 

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In the formulas, Rs, a, R 7 , R1, R 2 , R 3 , Y andx- are the same as defined above. Further, the plurality ofR, Rs, R $^{7 }$and a may be the same or different from each other 

The weight average molecular weight (Mw) (the polysty› rene equivalent value determined by gel permeation chroma› tography) of the component (Al’) is not particularly limited, but is preferably 1,000 to 50,000, more preferably 1,500 to 30,000, and most preferably 2,500 to 25,000. When the weight average molecular weight is no more than the upper limit of the above-mentioned range, the resist composition exhibits a satisfactory solubility in a resist solvent. On the other hand, when the weight average molecular weight is at least as large as the lower limit of the above-mentioned range, dry etching resistance and the cross-sectional shape of the resist pattern becomes satisfactory. 

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, more preferably 1.0 to 4.0, and most preferably 1.0 to 3.0. 

Here, Mn is the number average molecular weight 

In the component (A’), as the component (Al’), one type may be used, or two or more types of compounds may be used in combination. 

In the component (A’), the amount of the component (Al’) based on the total weight of the component (A’) is preferably 60 10 to 90% by weight, more preferably 20 to 80% by weight, and still more preferably 30 to 70% by weight. 

In the resist composition of the present invention, the com› ponent (A’) may contain "a base component which exhibits increased solubility in an alkali developing solution under action of acid" other than the component (Al’) (hereafter, referred to as "component (A2)"). 

(Al’-11) 

The component (A2) is not particularly limited, and any of the multitude of conventional base components used within chemically amplified resist compositions (e.g., base resins used within chemically amplified resist compositions for ArF excimer lasers or KrF excimer lasers, preferably ArF excimer lasers) can be used. For example, as a base resin for ArF excimer laser, a base resin having the aforementioned struc› tural unit (al) as an essential component, and optionally the aforementioned structural units (a2) to (a4) can be used. 

As the component (A2), one type ofresin may be used, or two or more types of resins may be used in combination. 

In the resist composition of the present invention, the amount of the component (A’) can be appropriately adjusted depending on the thickness of the resist film to be formed, and the like. 

<Component (B)> 

The positive resist composition of the present invention may further include an acid-generator component (B) (here- after, referred to as "component (B)") which generates acid upon irradiation of radial rays. 

When the positive resist composition of the present inven› tion includes the component (B), as the component (B), there is no particular limitation, and any of the known acid genera- tors used in conventional chemically amplified resist compo› sitions can be used. Examples of these acid generators are numerous, and include onium salt acid generators such as iodonium salts and sulfonium salts; oxime sulfonate acid generators; diazomethane acid generators such as bisalkyl or bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diaz› omethaues; nitrobenzylsulfonate acid generators; iminosul› fonate acid generators; and disulfone acid generators. 

As an onium salt acid generator, a compound represented by general formula (b-1) or (b-2) shown below can be used. 

[Chemical Formula 59] 

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In the formulas above, R 1 " to R 3 ", Rs" and R $^{611 }$each indepen› dently represent an aryl group or alkyl group, wherein two of R 1 " to R 3 " may be bonded to each other to form a ring with the sulfur atom; and R 4 " represents an alkyl group, a halogenated alkyl group, an aryl group or an alkenyl group which may have a substituent, with the provision that at least one of R 1 " to R 3 " represents anaryl group, and at least one ofRsi’ andR 6 " represents an aryl group. 1 3 

In formula (b-1 ), R " to R " each independently represents an aryl group or an alkyl group. In formula (b-1), two ofR 1 " to R 3 " may be bonded to each other to form a ring with the sulfur atom. 1 3 

Further, among R " to R ", at least one group represents an aryl group. Among R 1 " to R 3 ", two or more groups are pref› erably aryl groups, and it is particularly desirable that all of R 1 " to are aryl groups. 1 3 

The aryl group for R " to R " is not particularly limited. For example, an aryl group having 6 to 20 carbon atoms may be used in which part or all of the hydrogen atoms of the aryl 

(b-1) 

(b-2) 

