Some embodiments provide microelectronic fabrication methods in which a sacrificial pattern is formed on a substrate. A spacer formation layer is formed on the substrate, the spacer formation layer covering the sacrificial pattern. The spacer formation layer is etched to expose an upper surface of the sacrificial pattern and to leave at least one spacer on at least one sidewall of the sacrificial pattern. A first portion of the sacrificial pattern having a first width is removed while leaving intact a second portion of the sacrificial pattern having a second width greater than the first width to thereby form a composite mask pattern including the at least one spacer and a portion of the sacrificial layer. An underlying portion of the substrate is etched using the composite mask pattern as an etching mask.