Sulfonium salt monomer, polymer, chemically amplified resist composition, and pattern forming process

A sulfonium salt monomer having the formula (A):

• wherein n1 is 0 or 1, n2 is 1, 2, 3 or 4, n3 is 1 or 2, n4 is 0, 1 or 2, n2+n3+n4 is from 0 to 5 when n1 is 0, n2+n3+n4 is from 0 to 7 when n1 is 1, n5 is 0 or 1, n6 is 1, 2, 3 or 4, n7 is 0, 1 or 2, n6+n7 is from 0 to 5 when n5 is 0, n6+n7 is from 0 to 7 when n5 is 1, n8 is 1 or 2,
• RF is fluorine, a C1-C6 fluorinated saturated hydrocarbyl group, a C1-C6 fluorinated saturated hydrocarbyloxy group, a C1-C6 fluorinated saturated hydrocarbylthio group, or a pentafluorosulfanyl group, Groups RF may be identical or different when n6 is 2, 3 or 4,
• R1 and R2 are each independently halogen exclusive of fluorine, nitro group, cyano group, hydroxy group, carboxy group, a C1-C20 hydrocarbyl group which may contain a heteroatom, a C1-C20 hydrocarbyloxy group which may contain a heteroatom, a C1-C20 hydrocarbylthio group which may contain a heteroatom, a plurality of R1 may be identical or different and two R1 may bond together to form a ring with the carbon atoms to which they are attached, when n4 is 2, a plurality of R2 may be identical or different and two R2 may bond together to form a ring with the carbon atoms to which they are attached, when n7 is 2,
• L1 is an ether bond, an ester bond, or a carbonate bond,
• RAL is an acid labile group,
• two of three aromatic rings bonded to S+ may bond together to form a ring with a sulfur atom to which they are attached, and
• Z− is a fluoroalkanesulfonate anion having a polymerizable group.