3  US 9,250,518 B2  4  However, it has only a little influence on performance  improvement. There is a desire to have a quencher for further  improving contrast.  Patent Document 4 discloses an amine quencher which  reduces its basicity through a mechanism that an acid labile  group is eliminated under the action of acid, and lactam is  then formed. Due to the mechanism that basicity is reduced  under the action of acid, acid diffusion is controlled by high  basicity in the unexposed region where the amount of acid  generated is minimal, whereas acid diffusion is promoted due  to reduced basicity of the quencher in the overexposed region  where the amount of acid generated is large. This expands the  difference in acid amount between the exposed and unex› posed regions, from which an improvement in contrast is  expected. However, the contrast enhancing effect is low since  deprotection reaction of the base polymer and deprotection  reaction of the quencher and ensuing lactam-forming reaction  take place simultaneously in parallel. If the deprotection reac› tion of the quencher is slower than the deprotection reaction  of the base polymer, the contrast enhancing effect is lower.  There is a desire to have a quencher capable of further contrast  improvement.  A blend of an onium salt of a-non-fluorinated sulfonic acid  or carboxylic acid with an onium salt of a-fluorinated sul› fonic acid, imidic acid or methidic acid is effective for reduc› ing LWR, but suffers from a low dissolution contrast.  An  amine compound quencher provides a high dissolution con› trast, but is less effective for reducing LWR. There is a desire  to have a quencher which offers a high dissolution contrast  and reduced LWR.  An  object of the invention is to provide a resist composition 45  which exhibits a high dissolution contrast and reduced LWR  independent of whether it is positive or negative working; and  a pattern forming process using the same.  The inventors have found that a resist composition com› prising a sulfonium or iodonium salt of a carboxylic acid  having an acid-reactive group of specific structure is used to  form a photoresist film having a high contrast and minimal  LWR.  In one aspect, the invention provides a resist composition  comprising a base polymer and a sulfonium salt having the  general formula (1 )-1 or a iodonium salt having the general  formula (1)-2.  Herein R  1  is hydrogen, or a straight, branched or cyclic  C$_{1 }$-C$_{30 }$ alkyl,  CcC$_{30 }$ aryl, C$_{7}$ -C$_{30 }$ aralkyl, C$_{2}$ -C$_{30 }$ alkenyl,  C$_{2}$-C$_{10 }$ alkynyl, or C$_{4}$ -C$_{12 }$heterocyclic-bearing group, or a  combination of such groups, which group may contain a  hydroxyl, mercapto, carboxyl, ether, thio ether, ester, sulfonic  acid ester, sulfonyl, lactone ring, carbonyl, cyano, nitro, halo› gen, trifluoromethyl, amide, imide, sulfonamide, carbonate,  sulfide, -N=CR---0-, -N=CR-S-, or  N-O› N=moiety, or R $^{1 }$may be an acid labile group; R is hydrogen,  mercapto, hydroxyl or C$_{4}$ -C$_{3 }$ alkyl, or may bond with the  nitrogen atom in formula (1) to form a ring; R $^{2 }$and R$^{3 }$each are  hydrogen, a straight or branched C$_{1 }$-C$_{4 }$ alkyl group or C$_{2}$-C$_{4 }$ alkenyl group, or R$^{2 }$andR$^{3 }$may bond together to form a ring  with the carbon atom to which they are attached; R 4 ,  Rs and  R  6  are each independently a straight, branched or cyclic  C$_{1 }$-C$_{12 }$alkyl, alkenyl, oxoalkyl or oxoalkenyl group,  CcC$_{20 }$ aryl, C$_{7}$-C$_{12 }$aralkyl or aryloxoalkyl group, in which at least  one hydrogen atom may be substituted by an ether, ester,  carbonyl, carbonate, hydroxyl, carboxyl, halogen, cyano,  amide, nitro, sultone, sulfonic acid ester, sulfone moiety, or  sulfonium salt-containing substituent, R 4  and Rs may bond  together to form a ring with the sulfur atom to which they are  attached; R$^{7 }$and R$^{8 }$each are a C$_{6}$-C$_{20 }$aryl group which may  contain a straight, branched or cyclic C$_{1 }$-C$_{10 }$alkyl or alkoxy  moiety, and m is an integer of 2 to 8.  The resist composition may further comprise an acid gen› erator capable of generating a sulfonic acid, imidic acid or  methidic acid.  In a preferred embodiment, the base polymer comprises  recurring units (al) derived from (meth)acrylate, styrenecar› boxylic acid or vinylnaphthalenecarboxylic acid having an  acid labile group substituted thereon, or recurring units (a2)  derived from hydroxystyrene having an acid labile group  substituted thereon, as represented by the general formula (2):  wherein R 9  and R  11  are each independently hydrogen or  methyl, Xis a single bond, a C$_{1}$-C$_{12 }$linking group having an  ester moiety or lactone ring, phenylene group or naphthylene  group, Y is a single bond or ester group, and R $^{10 }$and R $^{12 }$are  each independently an acid labile group.  The resist composition may further comprise an organic  solvent, the resist composition being a chemically amplified  positive resist composition. Further a dissolution inhibitor  may be added.  CITATION LIST  DISCLOSURE OF INVENTION  -continued  Patent Document 1: JP-A 2001-194776  Patent Document 2: JP-A 2002-226470  Patent Document 3: JP-A 2002-363148  Patent Document 4: JP-A 2012-137729 (US 20120141938)  Non-Patent Document 1: SPIE Vol. 5039 pl (2003)  Non-Patent Document 2: SPIE Vol. 6520 p65203L-1 (2007)  Non-Patent Document 3: SPIE Vol. 7639 p76390W (2010)  (1)-1  (1)-2  (2) 