Abstract: A semiconductor light emitting device includes a substrate, an n-type layer formed of gallium-nitride based compound semiconductor formed on the substrate, and a p-type layer formed of gallium-nitride based compound semiconductor formed on the substrate. Semiconductor overlying layers are constituted by the n-type layer and the p-type layer on the substrate. A light emitting layer is formed together with the n-type and p-type layers in the semiconductor overlying layers to emit light. At least one of the n-type layer and the p-type layer is formed by three or more overlying sublayers including a sublayer of AlyGa1-yN (0<y≦0.5) and a sublayer of AluGa1-uN (0≦u<y). With this structure, the semiconductor light emitting device is almost free from lattice mismatch to thereby enhance electron mobility and hence light emission efficiency even where the overlying semiconductor layers are different in lattice constant from the substrate.