A self-aligned platinum-silicide nanowire for biomolecule sensing is developed in this work, The 40 nm nanowire is fabricated through a sequence of electron-beam writing on the polysilicon film, line shrinkage with alkaline solution, platinum film deposition, 550 degrees C annealing, and aqua regia dissolution. The immobilization of single-stranded capture DNA onto the platinum-silicide nanowire is verified from the fluorescence-labeled technique, The field-effect transistor can distinguish the complementary, mismatched, and denatured DNA via the conductance difference. Although the nanowire sensor has not been integrated into a fluid channel system, we can sense the minimal target DNA concentration down to 100 fM, and the signal is still 1000-fold larger than the noise signal. (c) 2005 American Vacuum Society.