For example, a thickness of the upper layer in contact with the first active layer 121 of the first thin film transistor 120 may be greater than the thicknesses of the lower layer and the intermediate layer of the first buffer layer 111. For example, when the first buffer layer 111 is a quintuple layer as shown in FIG. 4, the 1-e buffer layer 111e in contact with the first active layer 121 may be an upper layer. In addition, the 1-a buffer layer 111a in contact with the substrate 110 may be a lower layer. In addition, the 1-b buffer layer 111b, the 1-c buffer layer 111c, and the 1-d buffer layer 111d that are disposed between the 1-a buffer layer 111a and the 1-e buffer layer 111e may be intermediate layers. Here, a thickness of the 1-e buffer layer 111e which is the upper layer may be greater than a thickness of the 1-a buffer layer 111a which is the lower layer and a thickness of each of the 1-b buffer layer 111b, the 1-c buffer layer 111c, and the 1-d buffer layer 111d which are the intermediate layers. However, the present disclosure is not limited thereto.
