Methods of forming metal oxide structures and methods of forming metal oxide patterns on a substrate using a block copolymer system formulated for self-assembly. The metal oxide structures and patterns may be used, for example, as a mask for sublithographic patterning during various stages of semiconductor device fabrication. A block copolymer at least within a trench in the substrate and including at least one soluble block and at least one insoluble block may be annealed to form a self-assembled pattern including a plurality of repeating units of the at least one soluble block laterally aligned with the trench and positioned within a matrix of the at least one insoluble block. The self-assembled pattern may be exposed to a metal oxide precursor that impregnates the at least one soluble block. The metal oxide precursor may be oxidized to form a metal oxide. The self-assembled pattern may be removed to form a pattern of metal oxide lines on the substrate surface.