MANUFACTURE OF FIELD EFFECT TRANSISTOR

摘要

PURPOSE:To decrease leaking current from a gate to a large extent, by providing the first process, by which a tantalum layer having a specified shape is formed on an insulating substrate; the second process, by which an insulating layer is formed on the tantalum layer and a gate insulating layer is obtained; and the third process, by which anodic oxidation of the tantalum layer is performed. CONSTITUTION:A tantalum layer is formed on a glass plate, which is coated with silicon dioxide. Minute machining is performed no the tantalum layer. A silicon nitride layer is formed on the tantalum layer by a plasma chemical vapor deposition method. A silicon dioxide layer is formed by a chemical vapor deposition method. An aluminum oxide layer is formed by a sputtering method. A tantalum oxide layer is formed by a sputtering method. Thus an insulating layer 3 is obtained. Then device is immersed in aqueous solution of phosphoric acid. A positive DC voltage is applied to the tantalum layer, and anodic oxidation is carried out. Then, aluminum is evaporated. Minute machining is carried out by a photolithography method and a wet etching method. Thus source and drain electrode 5 are obtained. The overlapping area of the gate electrode comprising the tantalum layer 2 and the drain electrode and the overlapped area of the gate electrode and the drain electrode are 250 square mum. Thus, the characteristics of an FET are improved, and the manufacturing yield rate is improved.