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[0178] As is evident from Tables 7 to 9, the positive resist compositions within the scope of the invention show satis› factory results including a DOF value of 150 or higher, a LWR value of2.6 to 3.1, and a size change by PED ofup to 2.7%. By contrast, the comparative positive resist compo› sitions are inferior in all of DOF, LWR and PED stability. 

[0179] Japanese Patent Application No. 2019-040330 is incorporated herein by reference. 

[0180] 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. 

1. A positive resist composition comprising: 

(A) 4.1 to 20 parts by weight of a first onium salt having the formula (1 ), 

(B) 2.3 to 8.8 parts by weight of a second onium salt having the formula (2), 

(C) 80 parts by weight of a base polymer adapted to increase alkaline solubility under the action of acid, the base polymer comprising acid labile group-containing recurring units having the formula (a) and optionally acid labile group-containing recurring units having the formula (b ), with the proviso that when the acid labile group-containing recurring units having formula (b) are included, those recurring units containing an acid labile group of at least 14 carbon atoms may be included in an amount of up to 5 mo! % of the overall recurring units, and 

(D) 200 to 5,000 parts by weight of an organic solvent, 

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wherein R 1 and R 2 each are a hydroxyl group or a C$_{1}$-C$_{30 }$ monovalent hydrocarbon group which may contain a het› eroatom, R forms an aliphatic ring of 4 or 5 carbon atoms with S+, m and n each are O or 1, k is O or 1, and z- is an organic anion, 

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wherein A $^{1 }$is hydrogen or trifluoromethyl, R $^{11 }$is a nitrogen› containing heterocyclic group or a group having the formula (2-1 ): 

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wherein R $^{12 }$and R $^{13 }$are each independently hydrogen or a C$_{1 }$-C$_{20 }$monovalent hydrocarbon group which may contain a heteroatom, R$^{12 }$and R$^{13 }$may bond together to form a ring with the nitrogen atom to which they are attached, R $^{14 }$is a C$_{1 }$-C$_{20 }$ divalent hydrocarbon group which may contain a heteroatom, the broken line designates a valence bond, and MA+ is a sulfonium cation having the formula (2A) or iodonium cation having the formula (2B): 

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wherein R 101 , R 102 , R 103 , R $^{104 }$and R$^{105 }$are each indepen› dently a C$_{1 }$-C$_{20 }$monovalent hydrocarbon group which may contain a heteroatom, any two or more of R 101 , R $^{102 }$and R $^{103 }$may bond together to form a ring with the sulfur atom to which they are attached, 

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