Plasma-polymerized C-60 thin films were investigated in the form of a field effect transistor (FET) structure. In the FET device, the C-60 polymer acts as a p-type semiconductor, whereas C-60 is an n-type semiconductor. Its conduction mechanism can be described as due to variable range hopping. As a sensing device, the C-60 polymer can behave as a gas sensor for electrophoric gases and can also be operated as a photo-sensing device in air.