A porous Si (PS) layer transfer process that monocrystalline Si film grown on a Si substrate wafer is separated with the substrate and transferred to a non-Si device realizes to get monocrystalline Si film on low-cost substrates such as glass. PS film is fabricated by electrochemical etching in a chemical mixture of HE and ethanol. Effect of ultrasonic frequency on surface morphology of PS film is studied. By applying ultrasonic waves during etching, the pores on PS film with uniform size can be fabricated. (C) 2010 Elsevier B.V. All rights reserved.