A field effect transistor in which a continuous semiconductor layer comprises: a) an organic semiconductor; and, b) an organic binder which has an inherent conductivity of less than 10.sup.-6Scm.sup.-1 and a permittivity at 1,000 Hz of less than 3.3 and a process for its production comprising: coating a substrate with a liquid layer which comprises the organic semiconductor and a material capable of reacting to form the binder; and, converting the liquid layer to a solid layer comprising the semiconductor and the binder by reacting the material to form the binder.