Photoresist compositions and methods of fabricating a semiconductor device

A photoresist composition comprising:

• a photosensitive polymer;
• a photoacid generator (PAG);
• a basic quencher;
• and
• a solvent,
• wherein the photosensitive polymer is a random copolymer comprising a first repeating unit having a structure of Chemical Formula 1, a second repeating unit having a structure of Chemical Formula 2, and a third repeating unit having a structure of Chemical Formula 3:
• wherein R1 is hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 15 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a cycloalkenyl group having 3 to 12 carbon atoms,
• R2 is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 15 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, or a carboxylate group having 1 to 6 carbon atoms,
• R3 is hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkynyl group having 2 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an aryl group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 7 carbon atoms, or a cycloalkenyl group having 3 to 7 carbon atoms,
• R4a is hydrogen, a hydroxyl group, a carboxyl group, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms, R4b is a hydroxyl group or a carboxyl group, and
• R2a is a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a halogen atom, or a linear or branched alkyl halide group having 1 to 6 carbon atoms, and R2b is an acid-labile protecting group.