Thin film transistor substrate, LCD device including the same, and method for manufacturing thin film transistor substrate

A thin film transistor substrate, comprising:

• a base substrate;
• and
• a thin film transistor having a gate electrode provided on the base substrate, a gate insulating film provided so as to cover the gate electrode, a semiconductor layer comprised of an oxide semiconductor and provided on the gate insulating film so as to overlap the gate electrode, and a source electrode and a drain electrode which are provided on the gate insulating film so as to face each other on the semiconductor layer and so that a part of the source electrode and a part of the drain electrode are connected to the semiconductor layer, wherein
• the source electrode and the drain electrode have a stack of a first conductive layer, a second conductive layer, and a third conductive layer,
• the third conductive layer is comprised of a low resistance metal that causes a redox reaction with the oxide semiconductor,
• the first conductive layer directly contacts the semiconductor layer, is formed by dry etching, and is comprised of a refractory metal including a Group 4 metal element that is less likely to cause the redox reaction with the oxide semiconductor than the third conductive layer does, an alloy primarily containing the Group 4 metal element, or a nitride or oxide thereof,
• the second conductive layer is comprised of a refractory metal including a Group 5 or Group 6 metal element into which metal particles of the third conductive layer are less likely to diffuse than into the first conductive layer, an alloy primarily containing the Group 5 or Group 6 metal element, or a nitride or oxide thereof, and
• the semiconductor layer is formed by performing annealing in an oxygen-containing atmosphere after formation of the source electrode and the drain electrode.