Thin film transistor structure for a field emission display and the method for making the same

A thin film transistor structure for a field emission display, comprising:

• a substrate having a semiconductor area for forming a thin film transistor;
• a patterned poly-silicon layer having a source area, a drain area, and a channel on the semiconductor area of the substrate, wherein the source area and the drain area are doped with ions, and the channel is sandwiched in between the source area and the drain area;
• a patterned first gate metal layer located on the poly-silicon layer;
• a first gate-insulating layer sandwiched in between the poly-silicon layer and the first gate metal layer;
• a patterned second gate metal layer located on the poly-silicon layer;
• and
• a second gate-insulating layer sandwiched in between the poly-silicon layer and the second gate metal layer;
• wherein the thickness of the second insulating layer is greater than that of the first gate-insulating layer, and the absolute voltage in the channel under the first gate metal layer is less than that under the second gate metal layer when a voltage higher than the threshold voltage thereof is applied to both of the first gate metal layer and the second gate metal layer.