A semiconductor light emitting device includes a substrate; a light emitting structure and a Zener diode structure disposed to be spaced apart from each other on the substrate, and including a first semiconductor layer and a second semiconductor layer, respectively; and a common, integrally formed, electrode electrically connected to the first semiconductor layer of the light emitting structure and the second semiconductor layer of the Zener diode structure. At least a portion of the Zener diode formed by the Zener diode structure is disposed below the common electrode.