A dielectric film layer structure and a fabricating method thereof are provided. The dielectric film layer structure at least has a first capacitor electrode, a dielectric layer, and a second capacitor electrode, wherein the dielectric layer includes two materials of SiNx and SiOx. In a place where voltage drop is relatively large, the dielectric layer is mainly made of SiNx, and in a place where the voltage drop is relatively small, the dielectric layer is mainly made of SiOx, thereby changing current for charging thin film transistors, reducing influence of the voltage drop, and improving uniformity of panel voltage output.