21  US 9,291,896 B2  22  -continued  In formulae  (1-1) to (1-4),  R’, Ria, Ri$_{6}$ ,  Ric, R$_{2 }$ andR$_{3 }$have  the same meanings as R’, Ria, Ri$_{6}$ ,  Ric, R$_{2 }$ and R$_{3 }$ in formula  (1  ),  respectively.  At least two of Ria, Ri$_{6 }$ and Ric may combine with each  other to form a ring, or at least one of Ria, Ri$_{6 }$ and Ric may  combine with R$_{2 }$ to form a ring.  From the standpoint of more unfailingly realizing high  contrast (high  y  value) and more reliably achieving enhance› ment of the resolution and sensitivity at the formation of a fine  isolated pattern as well as formation of a rectangular pattern  profile, the content of the repeating unit represented by for› mula  (1 ), (1-1  ), (1-2), (1-3) or  (1-4)  in the resin (P) (in the case  of containing a plurality of kinds, the total thereof) is prefer› ably  10  mo!% or more, more preferably  14  mo!% or more,  based on all repeating units in the resin (P).  The upper limit is not particularly limited, but from the  standpoint of ensuring the content of the later-described  repeating unit represented by formula (A) and more unfail› ingly achieving enhancement of the resolution and sensitivity  at the formation of a fine isolated pattern as well as formation  of a rectangular pattern profile, the content is preferably 85  mo! % or less, more preferably 80 mo! % or less.  Specific examples of the repeating unit represented by  formula  (1), (1-1),  (1-2), (1-3) or  (1-4)  are illustrated below,  but the present invention is not limited thereto.  In specific examples, Xa represents a hydrogen atom, CH$_{3}$ ,  CF$_{3 }$ orCH$_{2}$OH.  (1-4)  Xa  ,:(  -continued 