A thin-film transistor includes a gate, a first source, a second source, a first drain, a second drain, a first semiconductor layer, a second semiconductor layer, a first insulation layer, and a second insulation layer. The gate includes a first surface and a second surface that are opposite to each other. The first insulation layer is formed on the first surface and covers the first surface. The first semiconductor layer is formed on the first insulation layer. The first drain and the first source are formed on the first semiconductor layer in a spaced manner. The second insulation layer is formed on the second surface and covers the second surface. The second semiconductor layer is formed on the second insulation layer. The second drain and the second source re formed on the second semiconductor layer in a spaced manner. Also disclosed are an array substrate and a display device.