Abstract: Our Si based thin fuel cells have a through-chip porous Pt layer. The through-chip porous area has long narrow shape and the through-chip porous layer sometimes cracked during experimental handling. Therefore, the fuel channel shape was changed to square shape. Si substrate around the through-chip porous area works as rims and the mechanical strength seemed to be improved. Using the square openings, peak output of 108mW/cm 2 was obtained. However, the square opening is not suitable for our stacking structure. Then shallow channels, which connect each through-chip porous Pt layer, were fabricated by plasma etching with double masking layers
