A thin-film transistor (TFT) with high carrier mobility has been fabricated using poly(2,5-thienylenevinylene)(PTV) as semiconductor. The carrier mobility has been obtained to be 0.22cm(2)/Vsec, which is in the same level as that of amorphous silicon TFT. It has been indicated that the enlargement of the pi-conjugation length is crucial for the improvement of the carrier mobility. It has been also demonstrated that the molecular orientation is another important factor in terms of the device characteristics.