The present invention relates to a hybrid photoresist composition for improved resolution and a pattern forming method using the photoresist composition. The photoresist composition includes a radiation sensitive acid generator, a crosslinking agent and a polymer having a hydrophobic monomer unit and a hydrophilic monomer unit containing a hydroxyl group. At least some of the hydroxyl groups are protected with an acid labile moiety having a low activation energy. The photoresist is capable of producing a hybrid response to a single exposure. The patterning forming method utilizes the hybrid response to form a patterned structure in the photoresist layer. The photoresist composition and the pattern forming method of the present invention are useful for printing small features with precise image control, particularly spaces of small dimensions.