A nonvolatile read-only memory device, wherein a word line is on a substrate and the word line includes a metal layer and a polysilicon line. A trapping layer is further located between the word line and the substrate. A polysilicon protection line is formed over the substrate and the polysilicon protection line connects the word line and a grounded doped region in the substrate, wherein the resistance of the polysilicon protection line is higher than that of the word line.