A light emitting device comprising: a substrate ; a light extraction layer disposed on the substrate , the light extraction layer including a plurality of separated light extraction structures each including a plurality of layers , the lowermost layer of the plurality of layers disposed on the substrate and the uppermost layer of the plurality of layers disposed on the lowermost layer opposite to the substrate ; and a light emitting structure disposed on the substrate and the light extraction layer , the light emitting structure including a first conductivity type semiconductor layer , a second conductivity type semiconductor layer and an active layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer , such that the first conductivity type semiconductor layer contacts the uppermost layer and the substrate between the plurality of separated light extraction structures , wherein each of the light extraction structures includes a lower part defining a first region (al) contacting the substrate and an upper part opposite to the substrate defining a second region (a2), the first region (al) having a greater cross-sectional area than the cross-sectional area of the second region (a2), and wherein the refraction index of the light extraction layer is higher than that of the substrate and lower than that of the light emitting structure , characterised in that , each of the light extraction structures consist of the uppermost layer , the lowermost layer , and a middle layer between the uppermost layer and the lowermost layer , wherein the middle layer covers the upper and side surfaces of the lowermost layer , wherein the uppermost layer covers the upper and side surfaces of the middle layer , wherein the refraction index of the uppermost layer is higher than that of the middle layer , and wherein the refraction index of the middle layer is higher than that of the lowermost layer . a substrate ; a light extraction layer disposed on the substrate , the light extraction layer including a plurality of separated light extraction structures each including a plurality of layers , the lowermost layer of the plurality of layers disposed on the substrate and the uppermost layer of the plurality of layers disposed on the lowermost layer opposite to the substrate ; and a light emitting structure disposed on the substrate and the light extraction layer , the light emitting structure including a first conductivity type semiconductor layer , a second conductivity type semiconductor layer and an active layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer , such that the first conductivity type semiconductor layer contacts the uppermost layer and the substrate between the plurality of separated light extraction structures , wherein each of the light extraction structures includes a lower part defining a first region (al) contacting the substrate and an upper part opposite to the substrate defining a second region (a2), the first region (al) having a greater cross-sectional area than the cross-sectional area of the second region (a2), and wherein the refraction index of the light extraction layer is higher than that of the substrate and lower than that of the light emitting structure , characterised in that , each of the light extraction structures consist of the uppermost layer , the lowermost layer , and a middle layer between the uppermost layer and the lowermost layer , wherein the middle layer covers the upper and side surfaces of the lowermost layer , wherein the uppermost layer covers the upper and side surfaces of the middle layer , wherein the refraction index of the uppermost layer is higher than that of the middle layer , and wherein the refraction index of the middle layer is higher than that of the lowermost layer . <EOS>