Positive resist composition

A positive resist composition comprising:

• (A) a polymer having a silicon atom in a side chain thereof, which is insoluble or sparingly soluble in an aqueous alkali solution and becomes soluble in an aqueous alkali solution by an action of an acid;
• and
• (B) an acid generator capable of generating an acid on exposure to active light rays or a radiation, which is represented by the following formula (I):
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• wherein R1, R2, R3, R4, and R5, which are the same or different, each represent a hydrogen atom, a nitro group, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted acylamino group;
• at least two of R1, R2, R3, R4, and R5 may be taken together to form a cyclic structure;
• R6 and R7, which are the same or different, each represent a hydrogen atom, a cyano group, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group;
• Y1 and Y2, which are the same or different, each represent a substituted or unsubstituted alkyl group which may contain an ether linkage or a sulfide linkage or a substituted or unsubstituted alkenyl group provided that, when Y1 and Y2 each represent an alkyl group, (i) at least one of them is an alkyl group having a hydroxyl group, an ether linkage or a sulfide linkage or (ii) Y1 and Y2 each represent an alkyl group having 2 or more carbon atoms;
• at least one of R1, R2, R3, R4, and R5 and at least one of Y, and Y2 may be taken together to form a ring;
• at least one of R1, R2, R3, R4, and R5 and at least one of R6 and R7 may be taken together to form a ring;
• and the acid generator may consist of two or more structures represented by the following formula (I) linked up together at any one of R1, R2, R3, R4, R5, R6, and R7 or any one of Y1 and Y2 via a linking group;
• and X represents a non-nucleophilic anion.