THIN FILM TRANSISTOR

摘要

PURPOSE:To finely perform the gradation display and to enable a high-speed operation by a method wherein the semiconductor layer is made thinner and its resistivity is made sufficiently higher by forming the opposing side surfaces of source and drain electrodes each into a tapered surface. CONSTITUTION:The opposing side surfaces of a drain electrode 15a and a source electrode 19a are formed into tapered surfaces 31 and 32. Therefore, a semiconductor layer 21 is made sufficiently thinner, its resistivity is increased, the OFF-state resistance of a thin film transistor is hard to be affected by the external light, a large OFF-state resistance can be obtained and a light-shielding layer 25 can be omitted. Furthermore, ohmic contact layers 27 and 28 are formed over the whole surfaces of these tapered surfaces 31 and 32, and the semiconductor layer 22 and the electrodes 15a and 19a can be brought into an ohmic contact with each other over a sufficient area. Therefore, the characteristics of a drain current (a) us a drain voltage (b) become good ones having no offset as indicated by solid lines. Furthermore, the maximum drain current also is increased, a current can be supplied to a display electrode at high speed, a high speed operation becomes possible and furthermore, as the characteristics have no offset, the control range is wide in the case of the gradation display and moreover, the gradation display can be performed sufficiently and accurately.