Abstract: A field effect transistor comprising, as provided on a support substrate, an insulation layer, a gate electrode and an organic semiconductor layer separated by the insulation layer, a source electrode and a drain electrode provided so as to contact the organic semiconductor layer, wherein elongation ?1 (%) at the yield point of the insulation layer is larger than elongation ?2 (%) at the yield point of the support substrate.

Abstract: The mechanical characteristics of the support substrate and the insulation layer of an organic field effect transistor are optimized to thereby attain a high mobility, a high on-current and a low leak current, and a high on/off ratio in the organic field effect transistor. A field effect transistor comprising, as provided on a support substrate 1, an insulation layer 3, a gate electrode 2 and an organic semiconductor layer 4 separated by the insulation layer, a source electrode 5 and a drain electrode 6 provided so as to contact the organic semiconductor layer 4, wherein elongation ?1 (%) at the yield point of the insulation layer is larger than elongation ?2 (%) at the yield point of the support substrate. It has good flexible characteristics, whereby cracking, etc. due to a stress exerted will be suppressed, and a leak current will thereby be reduced, and thus, a high mobility, a high on-current and a low leak current, and a high on/off ratio can be attained.