A metal interconnection structure includes a substrate and a protective layer. The substrate includes at least a first conductive layer. The protective layer is a single-layered structure disposed on the substrate, and a quantity of oxygen (O) in an upper part of the protective layer is more than a quantity of oxygen (O) in a lower part of the protective layer. A material of the upper part of the protective layer includes silicon oxycarbide (SiCO) or silicon oxycarbonitride (SiCNO), and a material of the lower part of the protective layer includes silicon carbide (SiC) or silicon carbonitride (SiCN).