a chemically amplified photosensitive resin composition containing a first compound forming an acid by irradiation of actinic ray and a second compound that changes the solubility to an aqueous alkali solution with acid - catalyzed reaction wherein an ion dissociative compound having the composition represented by the general formula or , as well a method of forming a resist pattern using the composition are disclosed , the formulae being expressed by : where each of r 2 , r 3 and r 4 represents hydrogen , and an alkyl or aryl group of 1 to 7 carbon atoms , at least one of r 1 , r 2 , r 3 and r 4 represents hydrogen , y 1 represents chlorine , bromine , iodine , carbonate group of 1 to 7 carbon atoms or sulfonate group of 1 to 7 carbon atoms , and