A thin film field effect transistor is disclosed which provides improved time-based channel stability. The field effect transistor includes first and second disordered semiconductor layers separated by an insulator. In an embodiment a carrier injection terminal is provided in a thin semiconductor layer closest to the gate terminal. An electric field is established in the thin semiconductor layer. At sufficient field strength, the electric field extends into the second semiconductor layer, which is in contact with the source and drain terminals. At sufficient field strength a channel is established in the second semiconductor layer, permitting current to flow between source and drain terminals. Above a certain gate voltage, there is sufficient free charge is induced in the first semiconductor layer so that the field does not extend into the second semiconductor, effectively shutting off current between source and drain. Single-device transition detection (as well as other applications) may be obtained.