There is provided a biomolecule FET enhancing a sensitivity. The biomolecule FET includes a substrate, first and second impurity regions formed on both sides of the substrate, and doped with impurities of a polarity opposite to that of the substrate, a gate formed on the substrate and being in contact with the first and second impurity regions, and a probe biomolecule attached to the gate. A region of the gate adjacent to the first impurity region is wider than a region thereof adjacent to the second impurity region. A density of the probe biomolecule attached to the surface of the gate is increased, and when detecting a level of hybridization of the probe biomolecule and the target biomolecule, its sensitivity is improved.