Raman enhancement effect of the electrochemically roughened silicon substrate was studied with the excitation lines of 632.8 and 514.5 nm. Two kinds of Raman enhancement effects contributing to the overall Raman signal on the roughened silicon surfaces were found: the electromagnetic cavity resonance effect occurring on the particles at the submicron scale, and the resonant Raman effect occurring on the particles at the nanometer scale. The originally extremely weak fourth-order multiphonon band has been detected easily from the silicon nano-/micro-structures assisted by these enhancements. (C) 2003 Elsevier B.V. All rights reserved.