THIN FILM TRANSISTOR

PURPOSE:To set the drain current at a desired value by a method wherein the channel length-width ratio is changed without increasing the area of the TET by forming a roughness in the channel region between the source and drain electrodes. CONSTITUTION:A semiconductor layer 2 consisting of a-Si, for example, is formed on a light-transmitting substrate 1, such as a glass substrate. Then, a source electrode 3 and a drain electrode 4 are formed on the side of a first main surface 21 of the semiconductor layer 2 and a gate electrode 6 is formed on the side of a second main surface 22 of the semiconductor layer through a gate insulating film 5. Moreover, the gate electrode 6 is connected to a gate bus and a signal bus and the drain and source electrodes 4 and 3 are each connected to each transparent display electrode 7. A roughness is formed in the channel region between the source and drain electrodes 3 and 4 in the direction of a channel width W, but this is caused by triangular pillar-like oxide films 10 between the transparent substrate 1 and the gate electrode 6.