Silicon/Porous Silicon (Si/PS) composite membranes can be fabricated by converting a part of the silicon membrane thickness into porous silicon (PS) with electrochemical etching in HF based electrolyte. In this paper we discuss the performance of composite membranes with MacroPS for pressure sensors. The sensitivity of the composite membrane is found to be higher compared to silicon and improves with the increase in the porosity due to the drastic reduction in Young's Modulus of PS with porosity. The sensor response is found to be linear for pressures below 1 bar. PS formation produces stress in the membrane raising the offset voltage in the pressure sensors. © 2007 IEEE.