In this work, barrier height inhomogeneity and its origin are investigated for Au and Cu/n-InP metal/semiconductor contacts. The effective barrier height values of the Au and Cu/n-InP Schottky barrier diodes (SBDs) have been obtained as 0.480 and 0.404eV from current-voltage (I-V) characteristics using the thermionic emission theory. The barrier height values of the Au and Cu/n-InP SBDs have been obtained as 0.524 and 0.453 eV from the experimental reverse bias capacitance-voltage (C-V) characteristics, respectively. The discrepancy between the barrier heights could be explained in terms of barrier height inhomogeneity approach. To investigate origin of the barrier height inhomogeneity, the interface atomic concentration and its distribution have been obtained by deep profile analysis using electron spectroscopy for chemical analysis (ESCA) data. The analysis shows that the interface is not abrupt. Thus, we could say lateral barrier height inhomogeneity could arise from the interface inhomogeneity. (C) 2009 Elsevier B.V. All rights reserved.