Negative photosensitive composition and pattern formation method

A negative photosensitive composition comprising:

• an epoxy group-containing resin (A);
• and
• a cationic polymerization initiator (B) which comprises at least one cationic polymerization initiator (B0) selected from the group consisting of compounds represented by general formula (b0-1) and compounds represented by general formula (b0-2), and a cationic polymerization initiator (B1) which generates an acid having a pKa of −3 or more,
• wherein a ratio between the cationic polymerization initiator (B0) and the cationic polymerization initiator (B1) is 5 to 200 as a mass ratio represented by component (B0)/component (B1), and
• the cationic polymerization initiator (B1) comprises at least one compound selected from the group consisting of compounds represented by general formula (b1-1′) and compounds represented by general formula (b1-2′):
• wherein Rb01 to Rb04 are each independently a fluorine atom or an aryl group which may have a substituent, Rb05 is a fluorine atom or a fluorinated alkyl group which may have a substituent, plural Rb05's may be the same as or different from each other, q is an integer of 1 or more, and Qq+'s are each independently a q-valent organic cation;
• and
• wherein Rb11 and Rb12 each are a cyclic group which may have a substituent other than a halogen atom, a chain alkyl group which may have a substituent other than a halogen atom, or a chain alkenyl group which may have a substituent other than a halogen atom, R201 to R203 each independently represent an aryl group which may have a substituent, a heteroaryl group, an alkyl group, or an alkenyl group, and R201 to R203, may be bonded to each other to form a ring with the sulfur atom in the formula, provided that at least one of R201, R202, and R203 is an organic group having 16 or more carbon atoms.