Thin film transistor having semiconductor active layer

A thin film transistor, comprising:

• a substrate;
• an IGZO active layer on the substrate, the IGZO active layer, an atomic % of In in the IGZO active layer being between 55 atomic % and 75 atomic %, and an atomic % of Ga in the IGZO active layer being at least 10 atomic %, and the IGZO active layer including a channel region, a source region, and a drain region;
• a gate electrode overlapping the channel region and insulated from the IGZO active layer by a gate insulator;
• and
• source and drain electrodes contacting the source and drain regions, respectively,
• wherein the IGZO active layer is formed by:
• depositing ions including In, Ga, and Zn from a first target including In, Ga, and Zn;
• and
• depositing ions including In from a second target having a different atomic composition from the first target, the second target including InZnO, and
• controlling the deposition of ions from the second target so as to adjust an atomic % of In in the IGZO active layer to be between 55 atomic % and 75 atomic %.