Thin film transistor and method for manufacturing the same, display substrate, and display device

A thin film transistor, disposed on a base substrate, wherein the thin film transistor comprises:

• a first active layer, disposed on a side of the base substrate;
• a first gate, disposed on a side of the first active layer away from the base substrate;
• a first insulating layer, disposed on a side of the first gate away from the base substrate;
• a source and a drain, disposed on a side of the first insulating layer away from the base substrate, the source and the drain being electrically connected to the first active layer,
• wherein the first gate comprises a stacked structure comprising:
• a first conductive layer;
• and
• a first barrier layer, disposed on a side of the first conductive layer away from the base substrate,
• wherein a side of the first barrier layer away from the base substrate is in direct contact with a side of the first insulating layer proximate to the base substrate;
• and
• wherein the first barrier layer comprises TiNx1, wherein 0<x1<0.2, and x1 is a molar ratio of N to Ti;
• wherein the stacked structure of the first gate further comprises:
• a second barrier layer, disposed between the first conductive layer and the first barrier layer, wherein the second barrier layer comprises TiNx2, and a material of the second barrier layer has a higher N content than that of a material of the first barrier layer, wherein 0.5≤x2<0.8, and x2 is a molar ratio of N to Ti;
• and
• wherein the first barrier layer has a first grain size, the second barrier layer has a second grain size, and the first grain size is smaller than the second grain size.