A monomer having formula (A) is provided. RA is H, methyl or trifluoromethyl, X1 is a single bond, ether, ester or amide bond, Ra is a C1-C20 monovalent hydrocarbon group, Rb is H or an acid labile group, X is halogen, n is an integer of 1 to 4, m is an integer of 0 to 3, and 1≤n+m≤4. A resist composition comprising a polymer derived from the monomer has a high sensitivity to high-energy radiation, especially EUV.