Photoresist compositions and pattern formation methods

A pattern formation method, comprising:

• (a) applying a layer of a photoresist composition on a substrate;
• (b) pattern-wise exposing the photoresist composition layer to activating radiation;
• and
• (c) developing the exposed photoresist composition layer to provide a resist relief image,
• wherein the photoresist composition comprises:
• a first polymer comprising a first repeating unit comprising a hydroxy-aryl group and a second repeating unit comprising an acid-labile group, wherein the first polymer does not comprise a lactone group;
• a second polymer comprising a first repeating unit comprising a hydroxy-aryl group, a second repeating unit comprising an acid-labile group, and a third repeating unit comprising a lactone group;
• a photoacid generator;
• and
• a solvent.