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It is demonstrated in Tables 1 and 2 that resist composi› tions comprising a sulfonium or iodonium salt of iodinated phenoxy or iodinated phenylalkoxy-containing fluorinated sulfonic acid within the scope of the invention offer a high sensitivity and improved LWR and CDU. 

Japanese Patent Application No. 2016-155516 is incor› porated herein by reference. 

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

The invention claimed is: 

1. A resist composition comprising a base polymer and an acid generator containing a sulfonium salt having the for› mula (1-1) or an iodonium salt having the formula (1-2): 

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(1-1) 

(1-2) 

wherein R 1 is each independently a hydroxyl, C$_{1 }$-C$_{20 }$ straight, branched or cyclic alkyl or alkoxy group, C$_{2}$ -C$_{20 }$ straight, branched or cyclic acyl or acyloxy group, fluorine, chlorine, bromine, amino, or alkoxycarbonyl-substituted amino group, 

R 2 is each independently a single bond or C$_{1}$-C$_{4 }$ alkylene group, 

R 3 is a single bond or C$_{1 }$-C$_{20 }$divalent linking group when p=l, or a C$_{1 }$-C$_{20 }$tri- or tetravalent linking group when p=2 or 3, the linking group optionally containing an oxygen, sulfur or nitrogen atom, 

Rf 1 to R:t4 are each independently hydrogen, fluorine or trifluoromethyl, at least one ofRf$^{1 }$to R:t4 being fluorine or trifluoromethyl, or Rf 1 and Rf 2 , taken together, may form a carbonyl group, 

R 4 , Rs, R 6 , R 7 and R 8 are each independently a C$_{1}$-C$_{12 }$ straight, branched or cyclic alkyl group, C$_{2}$ -C$_{12 }$ straight, branched or cyclic alkenyl group, CcC$_{20 }$ aryl group or C$_{7}$-C$_{12 }$ aralkyl or aryloxyalkyl group, in which at least one hydrogen may be substituted by a hydroxyl, carboxyl, halogen, cyano, oxo, amide, nitro, sultone, sulfone, or sulfonium salt-containing moiety, or in which an ether, ester, carbonyl, carbonate or sulfonic acid ester moiety may intervene in a carbon› carbon bond, or R 4 and Rs may bond together to form a ring with the sulfur atom to which they are attached, 

m is an integer of 1 to 5, n is an integer of O to 3, and p is an integer of 1 to 3. 

2. The resist composition of claim 1, further comprising an organic solvent. 

3. The resist composition of claim 1 wherein the base polymer comprises recurring units having the formula (al) or recurring units having the formula (a2): 

