PROBLEM TO BE SOLVED: To greatly reduce dislocations which pierce a compd. semiconductor crystal layer formed on a substrate. SOLUTION: A substrate A for a light emitting diode comprises a sapphire substrate 10, an undoped GaN buffer layer 11 formed thereon, and an n-type compd. semiconductor crystal layer 12 formed thereon. A device structure B of the light emitting diode comprises a first n-type GaN clad layer 13 having p-type electrodes 17 thereon, an undoped In0.2 Ga0.8 N active layer 14 and a second p-type GaN clad layer 15 having n-type electrodes 16 thereon, formed in this order on the crystal layer 12. Trapezoidal recesses 18 are formed at regions facing the electrodes 16 on the substrate 10, and an upper part 10a of each recess 18 has a thickness which is not greater than that of the first clad layer 13.