Array substrate and manufacturing method thereof, display panel and display device

A manufacturing method of an array substrate, comprising:

• forming a buffer layer on a base substrate, wherein the base substrate comprises a driving thin film transistor region and a switching thin film transistor region, the buffer layer contains oxygen, the buffer layer comprises a first buffer part located in the driving thin film transistor region and a second buffer part located in the switching thin film transistor region, the first buffer part has a first thickness, the second buffer part has a second thickness, and the second thickness is greater than the first thickness;
• forming a first semiconductor active layer of a driving thin film transistor on the first buffer part, and forming a second semiconductor active layer of a switching thin film transistor on the second buffer part;
• and
• performing an annealing process on the base substrate on which the first buffer part, the second buffer part, the first semiconductor active layer, and the second semiconductor active layer are formed,
• wherein the forming the buffer layer on the base substrate comprises:
• coating a buffer film layer on the base substrate, coating a photoresist thin film on the buffer film layer;
• performing an exposure process and a development process on the photoresist thin film by a patterning process to form a photoresist-partially-removed part, a photoresist-completely-retained part, and a photoresist-completely-removed region;
• the photoresist-partially-removed part being located in the driving thin film transistor region, the photoresist-completely-retained part being located in the switching thin film transistor region;
• removing a part of the buffer film layer under the photoresist-partially-removed part to form the first buffer part;
• and
• removing remaining photoresist of the photoresist-completely-retained part to form the second buffer part.