Thin film transistor substrate and manufacturing method thereof

A thin film transistor (TFT) substrate, comprising:

• a TFT comprising:
• a substrate;
• a buffer layer, configured to cover the substrate;
• a semiconductor layer, configured to cover a first part of the buffer layer, wherein a drain and a source are formed on the semiconductor layer;
• a gate insulating layer, configured to cover the semiconductor layer and a part of the first part of the buffer layer, wherein a gate is formed on the gate insulating layer;
• and
• a dielectric layer, configured to cover the gate insulating layer and the gate;
• a flat layer, configured to cover the TFT, the flat layer defining an opening hole corresponding to the drain of the TFT, wherein a part of the flat layer is retained in a bottom of the opening hole to form a flat layer sheet;
• a second insulating layer, located on the flat layer;
• a third metal layer, located on the second insulating layer;
• a third insulating layer, located on the third metal layer;
• a first metal layer, located on the third insulating layer;
• a first insulating layer, configured to cover the first metal layer and the opening hole;
• and
• a second metal layer, located on the first insulation layer to pass through the flat sheeting and electrically connect to the drain;
• wherein the source and the drain are pass through the dielectric layer and connected to the flat layer.