US Patent 10161901 Dual gate biologically sensitive field effect transistor

A biologically sensitive field effect transistor includes a substrate, a first control gate and a second control gate. The substrate has a first side and a second side opposite to the first side, a source region and a drain region. The first control gate is disposed on the first side of the substrate. The second control gate is disposed on the second side of the substrate. The second control gate includes a sensing film disposed on the second side of the substrate. A voltage biasing between the source region and the second control gate is smaller than a threshold voltage of the second control gate.