A method includes providing a substrate; forming a bottom layer over the substrate; forming a middle layer over the bottom layer, a top surface of which including a photosensitive moiety having a first end anchored in the middle layer and a second end extending away from the top surface of the middle layer; forming a photoresist layer over the middle layer; exposing the photoresist layer to a radiation source; and developing the photoresist layer to form a pattern. The photosensitive moiety, which includes one of a photo-acid generator (PAG), a photo-base generator (PBG), photo-decomposable base (PDB), or photo-decomposable quencher (PDQ), may be anchored to a polymer backbone forming the middle layer via one or more linker groups. A distance by which the photosensitive moiety extends into the photoresist layer may be determined by a length of the linker group.