Provided are a display substrate, a display device, and a method of manufacturing the display substrate. The display substrate includes: a substrate in which a pixel region is defined; a gate electrode and a gate pad are formed on the substrate; a gate insulating layer formed on the gate electrode and the gate pad; a buffer layer pattern overlaps the gate electrode and is formed on the gate insulating layer; an insulating film pattern formed on the buffer layer pattern; an oxide semiconductor pattern formed on the insulating film pattern; a source electrode formed on the oxide semiconductor pattern; and a drain electrode formed on the oxide semiconductor pattern and is separated from the source electrode.