A field effect transistor for detecting an analyte having a thiol group includes a substrate, a source region and a drain region formed apart from each other on the substrate, the source region and the drain region being doped such that a polarity of the source and drain region is opposite to a polarity of the substrate, a channel region disposed between the source region and the drain region, an insulating layer formed of an electrically insulating material and disposed on the channel region, a gold layer disposed on the insulating layer and a reference electrode disposed apart from the gold layer.