The present disclosure relates to a thin-film transistor, an array substrate, a display panel and a display device and fabrication methods thereof. The thin-film transistor includes a gate insulation layer, an active layer having a source region, a drain region, and a channel region, a first doping layer on the source region, a second doping layer on the drain region, and at least one third doping layer arranged between the first doping layer and the second doping layer, wherein the first, the second, and the third doping layers have same conductivity type, and wherein the third doping layer is positioned in the channel region and contacts the gate insulation layer, and the third doping layer does not contact the first doping layer and the second doping layer simultaneously, or the third doping layer is positioned on the channel region and only contacts the first or the second doping layer.