A novel photoacid generator containing a structure of the following formula (I), wherein R is a monovalent organic group with a fluorine content of 50 wt % or less, a nitro group, a cyano group, or a hydrogen atom, and Z1 and Z2 are individually a fluorine atom or a linear or branched perfluoroalkyl group having 1-10 carbon atoms, is provided. When used in a chemically amplified radiation-sensitive resin composition, the photoacid generator exhibits high transparency, comparatively high combustibility, and no bioaccumulation, and produces an acid exhibiting high acidity, high boiling point, moderately short diffusion length in the resist coating, and low dependency to mask pattern density.