Thin film field effect transistor and a method of manufacturing the same

Abstract

A thin film field effect transistor comprising a source electrode and a drain electrode joined to a first semiconductor layer respectively through first and second portions of a second doped semiconductor layer, a gate insulating layer, and a gate electrode capacity-coupled through the gate insulating layer with a portion of the first semiconductor layer, in which a channel is formed, corresponding to a gap between the source electrode and the drain electrode. A doped intermediate semiconductor layer is formed in contact with the channel in the first semiconductor layer. The gate threshold voltage of the thin film field effect transistor can be varied by selectively varying the thickness of the doped intermediate semiconductor layer. Thus, a plurality of thin film field effect transistors respectively having different gate threshold voltages can be formed on a single substrate simply by forming the doped intermediate semiconductor layers for the thin film field effect transistors with different thicknesses.