Provided are gap-fill methods. The methods comprise: (a) providing a semiconductor substrate having a relief image on a surface of the substrate, the relief image comprising a plurality of gaps to be filled, wherein the gaps have a width of 50 nm or less; (b) applying a gap-fill composition over the relief image, wherein the gap-fill composition comprises a first polymer comprising a crosslinkable group, a second polymer comprising a chromophore, wherein the first polymer and the second polymer are different, a crosslinker, an acid catalyst and a solvent, wherein the gap-fill composition is disposed in the gaps; (c) heating the gap-fill composition at a temperature to cause the first polymer to self-crosslink and/or to crosslink with the second polymer to form a crosslinked polymer; (d) forming a photoresist layer over the substrate comprising the crosslinked polymer-filled gaps; (e) patternwise exposing the photoresist layer to activating radiation; and (f) developing the photoresist layer to form a photoresist pattern. The methods find particular applicability in the manufacture of semiconductor devices for the filling of high aspect ratio gaps with an antireflective coating material.