Abstract: A chemically amplified photoresist composition comprising, (a) a compound which cures upon the action of an acid or a compound whose solubility is increased upon the action of an acid; and (b) as photosensitive acid donor, at least one compound of the formula Ia, Ib, Ic, IIb or IIc wherein R1 is for example C1-C5alkyl, C3-C30cycloalkyl, C1-C5haloalkyl, C2-C12alkenyl, C4-C8cycloalkenyl, C6-C12bicycloalkenyl, phenyl, naphthyl, anthracyl, phenanthryl, or is a heteroaryl radical; all of which are unsubstituted or substituted; optionally some of the substituents form 5- or 6-membered rings with further substituents on the phenyl, naphthyl, anthracyl, phenanthryl, or heteroaryl ring or with one of the carbon atoms of the phenyl, naphtyl, anthracyl, phenanthryl, or heteroaryl ring; R?1 is for example C1-C12alkylene, C3-C30cycloalkylene, phenylene, naphtylene, diphenylene, or oxydiphenylene, wherein these radicals are unsubstituted or substituted; A and B for example are a direct bond; Ar1 and Ar2 independently of ea