A novel miniature fuel cell is proposed with monolithically fabricated Si electrodes. We recently discovered that a porous Pt layer can be formed uniformly on Si substrate by immersing porous Si into a Pt plating bath containing HF. To exploit the porous Pt as a catalyst layer, we explored the conditions for porous Pt formation. After formation of the porous Pt catalyst layer on a Si wafer, fuel channels were opened by applying dry etching from the opposite side of the Si wafer until the etching had reached to the porous layer. The porous Pt layer could be used as a stopping layer for the dry etching, and a through-chip porous layer was obtained. Two such Si electrodes were hot-pressed onto either side of a polymer electrolyte membrane, and 230 mu m thick prototype cells were constructed. By feeding H-2 and O-2 to the anode and cathode side, respectively, we obtained power generation at a peak power density of 145 mW/cm(2). (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3545070]