A thin film transistor comprises a substrate, a gate electrode formed on the substrate, an electrically insulating layer covering the gate electrode, a channel layer made of a semiconductor material and formed on the electrically insulating layer, a source electrode formed on a first lateral side of the electrically insulating layer, and a drain electrode formed on an opposite second lateral side of the electrically insulating layer. The source electrode has an inner end covering a first outer end of the channel layer and electrically connecting therewith. The drain electrode has an inner end covering an opposite second outer end of the channel layer and electrically connecting therewith. An area of the channel layer adjacent to and not covered by one of the source electrode and the drain electrode has an electrical conductivity lower than the electrical conductivity of other area of the channel layer.