A thin film transistor which includes an insulative substrate, and a gate electrode, a gate insulating film, a semi-conductor film, a source electrode, and a drain electrode, which are all laminated in that order onto the insulating substrate in the form of an array. The gate electrode is made of tantalum, and the gate insulating film is formed into a double-layered construction of an anodized tantalum film and a silicon nitride film, while the semi-conductor film is provided at each intersection between the gate electrode and the source electrode.