It is an object of the invention to provide a thin film transistor and a method for producing the same, which will easily achieve self-aligned formation of a source/drain region without through processes under a vacuum or a low pressure or with no use of expensive equipment. An exemplary method for producing a thin film transistor according to the invention includes an aliphatic polycarbonate layer forming step of forming an aliphatic polycarbonate layer 50 that covers a gate electrode layer 40 disposed above a semiconductor layer 20 with a gate insulator 30 being interposed between the gate electrode layer 40 and the semiconductor layer 20, and also covers the semiconductor layer 20, and has a dopant causing the semiconductor layer 20 to become an n-type or p-type semiconductor layer, and a heating step of heating at a temperature causing introduction of the dopant into the semiconductor layer 20 and decomposition of the aliphatic polycarbonate layer 50.