We demonstrated that fluorescence XAFS measurements can reveal the local structures around dilute elements in thin semiconductor layers. In the GaAs samples doped with Er and O, majority of the Er atoms substituted Ga sublattices with adjacent two O atoms and two As atoms (Er-2O center). In the GaInN/GaN samples, it was shown that the segregation of InN phase occurred in the GaInN layer at a higher In-content (x = 0.30), although the segregation was not observed at a lower In-content (x = 0.05). XANES spectrum in the Tb-implanted SiO₂ sample was observed by detecting X-ray-excited visible luminescence. The spectrum was quite similar to that was measured by detecting fluorescence X-ray.