Feb.4,2021  100  US 2021/0033969 Al  [0101]  When used, the acid generator of addition type is  preferably added in an amount of  0.1  to 50 parts, and more  preferably  1  to  40  parts by weight per  100  parts by weight  of the base polymer.  [0102]  In case the acid generator is an acid generator-and› base polymer, this acid generator is a polymer, preferably  comprising recurring units derived from a compound  capable of generating an acid in response to actinic light or  radiation. In this case, the acid generator is preferably a base  polymer to be described below, specifically comprising  recurring units  (f) as essential unit.  [0103]  The chemically amplified resist composition of the  invention preferably contains a base polymer. Where the  resist composition is of positive tone, the base polymer  comprises recurring units containing an acid labile group,  preferably recurring units having the formula (al) and/or  recurring units having the formula (a2). These units are  simply referred to as recurring units (al) and (a2).  Base Polymer  (al)  -continued  -continued  j  0  ___r-{O_z_~F3  o---r- ’ Lso 3 - o 