The present invention provides an organic light-emitting diode display device and a manufacturing method thereof. An inorganic insulating layer covering a gate is formed, and an organic insulating layer is formed on the inorganic insulating layer, which prevents a problem of metal residue occurring in a subsequently formed metal layer during etching due to a steep slope. A groove is defined on a position of the organic insulating layer corresponding to the gate, and a metal component for forming a capacitor with the gate is formed in the groove and disposed corresponding to the gate.