Display device having a plurality of thin-film transistors with different semiconductors

A display device comprising:

• a substrate;
• a buffer layer disposed on the substrate;
• a first active layer disposed on the buffer layer, the first active layer made of poly-silicon;
• a first gate insulating layer disposed on the first active layer and the buffer layer;
• a second active layer disposed on the substrate, the second active layer made of oxide semiconductor;
• a second gate insulating layer disposed on the second active layer and the first gate insulating layer;
• a first gate electrode on the second gate insulating layer, the first gate electrode overlapping the first active layer;
• and
• a second gate electrode on the second gate insulating layer, the second gate electrode overlapping the second active layer,
• wherein the second gate insulating layer is continuously formed on the first gate insulating layer so that a first part of the second gate insulating layer overlapping with the first gate electrode and a second part of the second gate insulating layer overlapping with the second gate electrode are formed integrally with each other,
• wherein the first gate electrode and the second gate electrode are in direct contact with the second gate insulating layer.