US 10,725,377 B2  98  97  are not hydrogen at the same time, Rx and Ry may bond  together to form a ring with the carbon atom to which they  are attached, y is an integer of O to 2, u is O or 1, f is an  integer satisfying Osfs5+2y-g, and g is an integer of 1 to 3.  4.  A negative resist composition comprising (A) a sulfo- nium compound having the formula (A) and (B) a base  polymer containing a polymer comprising recurring units  having the formula (B 1 ),  wherein R1, R 2 , and R 3  are each independently a C$_{1}$-C$_{20 }$ straight, branched or cyclic monovalent hydrocarbon group  which may contain a heteroatom, p and q are each indepen- dently an integer of O to 5, r is an integer of O to 4, in case  of p=2 to 5, two adjoining groups R$^{1 }$may bond together to  form a ring with the carbon atoms to which they are  attached, in case of q=2 to 5, two adjoining groups R 2  may  bond together to form a ring with the carbon atoms to which  they are attached, in case of r=2 to 4, two adjoining groups  R 3  may bond together to form a ring with the carbon atoms  to which they are attached,  wherein the polymer further comprises recurring units  having the formula (B5):  wherein  RA  is as defined above, A 3  is a single bond or  C$_{1 }$-C$_{10 }$ straight, branched or cyclic alkylene group in  which an ether bond may intervene in a carbon-carbon  bond, R $^{15 }$is each independently halogen, an optionally  halogenated C$_{2}$ -C$_{8 }$ straight, branched or cyclic acyloxy  group, optionally halogenated C$_{1 }$-C$_{6 }$ straight, branched  or cyclic alkyl group, or optionally halogenated C$_{1 }$-C$_{6 }$ straight, branched or cyclic alkoxy group, W is hydro› gen, a C$_{1 }$-C$_{10 }$ straight, branched or cyclic monovalent  aliphatic hydrocarbon group in which an ether, carbo› nyl or carbonyloxy moiety may intervene in a carbon› carbon bond, or an optionally substituted monovalent  aromatic ring group, Rx and Ry are each independently  hydrogen, an optionally hydroxy or alkoxy-substituted  C$_{1 }$-C$_{15 }$ alkyl group or an optionally substituted mon› ovalent aromatic ring group, with the proviso that both  Rx and Ry are not hydrogen at the same time, Rx and  Ry may bond together to form a ring with the carbon  atom to which they are attached, y is an integer of O to  2, u is O or 1, f is an integer satisfying Of 5+2y-g, and  g is an integer of 1 to 3,  wherein the polymer further comprises recurring units of  at least one type selected from units having the formu› lae (al) to (a6):  (Bl)  (al)  (a2)  (a3)  wherein  RA  is hydrogen, fluorine, methyl or trifluorom› ethyl, R $^{11 }$is each independently halogen, an optionally 55  halogenated C$_{2}$-C$_{8 }$ straight, branched or cyclic acyloxy  group, optionally halogenated C$_{1 }$-C$_{6 }$ straight, branched  or cyclic alkyl group, or optionally halogenated C$_{1 }$-C$_{6 }$ straight, branched or cyclic alkoxy group, A $^{1 }$is a single  bond or C$_{1 }$-C$_{10 }$ straight, branched or cyclic alkylene  60  group in which an ether bond may intervene in a  carbon-carbon bond, s is O or 1, w is an integer of Oto  2, a is an integer satisfying Osas5+2w-b, and b is an  integer of 1 to 3,  65  (B5)  ¥01.  A3  R"l)j  /  I  y  [r  Ry  (A) 