In this paper, a new sensing device based on a FET structure having a PoSi layer as sensing material, namely adsorption porous silicon-based FET (APSFET), is proposed. The sensing mechanism is based on an gas-induced conduction channel in the crystalline silicon under the sensing layer, a new approach with respect to previously reported PoSi sensors. The fabrication process is based on a standard silicon process. In this work, the fabrication process along with an electrical characterization of the device in presence of different organic vapors (alcohols and acids) is presented and discussed. (C) 2003 Elsevier Science B.V. All rights reserved