MANUFACTURE OF FIELD EFFECT TRANSISTOR

摘要

PURPOSE:To reduce leaking current from a gate, by providing the first process, by which a tantalum layer having a specified shape is formed on an insulating substrate, and providing the second process, by which anodic oxidation of the surface of the tantalum layer is performed and a gate insulating film is obtained by heat treatment. CONSTITUTION:A tantalum layer is formed on a glass plate, which is coated with silicon dioxide. Minute machining is performed on the tantalum layer by a photolithography method and the like. Anodic oxidation of the tantalum layer is performed, and a tantalum oxide layer 3 is obtained. On the tantalum layer, the following layers are formed as gate insulating layers: a silicon nitride layer is formed by a plasma chemical vapor deposition method; a silicon oxide layer is formed by a chemical vapor deposition method; and a tantalum oxide layer is formed by a sputtering method. Then, as a material of a semiconductor layer 4, selenium is used. A selenium layer is formed for each sample by a resistance-heating evaporating method. Aluminum is evaporated. Minute machining is carried out, and source and drain electrodes 5 are obtained. The overlapping area of the gate electrode comprising the tantalum layer and the source electrode 5 and the overlapping area of the gate electrode and the drain electrode are 250 square mum. Thus, the FET, whose gate leaking current is very small, can be obtained.