Resist composition, compound for use in the resist composition and pattern forming method using the resist composition

A resist composition comprising (A) a sulfonium salt represented by the following formula (I);

• (D) a resin soluble in an alkali developer;
• and (E) an acid crosslinking agent capable of crosslinking with said resin soluble in an alkali developer under the action of an acid:
• wherein
• R1 represents an alkyl group or an aryl group,
• R2 to R9 each independently represents a hydrogen atom or a substituent and may combine with each other to form a ring,
• Z represents an electron-withdrawing divalent linking group,
• Xn− represents an n-valent organic anion,
• n represents an integer of 1 to 3, and
• m represents the number of anions necessary for neutralizing the electric charge;
• and wherein the acid crosslinking agent (E) is selected from the group consisting of:
• (1) phenol derivative acid crosslinking agents having a hydroxymethyl group, an alkoxymethyl group, or an acyloxymethyl group;
• and
• (2) acid crosslinking agents having an N-hydroxymethyl group, an N-alkoxy-methyl group or an N-acyloxymethyl group.

A sulfonium compound represented by formula (II):

• wherein
• R1 represents an aryl group,
• R2 to R9 each independently represents a hydrogen atom or a substituent and may combine with each other to form a ring,
• Z represents a sulfone group,
• Xn− represents an n-valent anion,
• n represents an integer of 1 to 3, and
• m represents the number of anions necessary for neutralizing the electric charge.

A sulfonium compound represented by formula (III):

• wherein
• R1 represents an alkyl group or an aryl group,
• R2 to R9 each independently represents a hydrogen atom or a substituent and may combine with each other to form a ring, provided that at least one of R1 to R9 contains an alcoholic hydroxyl group,
• Z represents an electron-withdrawing divalent linking group,
• Xn− represents an n-valent anion,
• n represents an integer of 1 to 3, and
• m represents the number of anions necessary for neutralizing the electric charge.