Provided are methods of trimming photoresist patterns. The methods involve coating a photoresist trimming composition over a photoresist pattern, wherein the trimming composition includes a matrix polymer, a free acid having fluorine substitution and a solvent, the trimming composition being free of cross-linking agents. The coated semiconductor substrate is heated to cause a change in polarity of the resist polymer in a surface region of the photoresist pattern. The photoresist pattern is contacted with a developing solution to remove the surface region of the photoresist pattern. The methods find particular applicability in the formation of very fine lithographic features in the manufacture of semiconductor devices.