Step-terrace structures on MOVPE grown InP(001) surface were investigated by using grazing X-ray scattering. After buffer layers were formed on the substrate, X-ray scattering profiles were measured in the same chamber without exposing the sample to air. Small peaks were observed at the tail of the specular reflections, suggesting the in-plane periodicity of surface morphology. The azimuth angle dependence of peak position suggests a one-dimensional structure on the surface, and considering the AFM images of the sample, the bunched step-terrace structure toward [100] is the reason of this structure. Analyses based on a simple grating approximation shows the period of the one-dimensional structure is about 550 nm, which is consistent with the spacing value determined from AFM images. (C) 2003 Elsevier Science B.V. All rights reserved.