layer 22 formed over the n type gan layer 21 and a p type gan layer 23 formed over the active layer 22 a separate buffer layer 24 may be formed between the n type gan layer 21 and the substrate 10 the active layer 22 may have a gan based single quantum well sqw structure a gan based multi quantum well mqw structure or a quantum structure for example a supper lattice of the gan based sqw or mqw structure the quantum structure of the active layer 22 may be formed using a combination of various gan based materials for example alingan ingan etc may be used the semiconductor layer 20 formed over the substrate 10 as described above may be mesa etched as shown in fig1 in order to divide unit device regions from one another the mesa etching may be carried out such that the n type gan layer 21 of the semiconductor layer 20 is exposed different from a trench etching which will be carried out such that the substrate 10 is exposed thus the mesa etching can be achieved within a time shorter than that of a general trench etching process thereafter p type electrodes 25 are formed on the gan semiconductor layer 20.