Method of manufacturing a semiconductor device comprising a field effect transistor

Abstract

The invention relates to a method of manufacturing a field effect transistor, in particular a discrete field effect transistor, comprising a source region (,) and a drain region (,) and, between said regions, a channel region (,) above which a gate region (,) is located. The gate region (,) is formed by applying an insulating layer (,) to the semiconductor body and providing this insulating layer with a stepped portion (,) in the thickness direction, whereafter a conductive layer (,) is applied to the surface of the semiconductor body (,), which layer is substantially removed again by etching, so that a part (,A) of the conductive layer (,), which part forms part of the gate region (,) and which lies against the stepped portion (,), remains intact. In a method in accordance with the invention, the source region (,) and the drain region (,) are formed before the insulating layer (,) is provided, and after the provision of the part (,A) of the gate region (,), which part is formed from the conductive layer (,), the surface of the semiconductor body (,) is made flat by applying a further insulating layer (,) next to the stepped portion (,). Such a method enables a T-shaped gate region (,) to be manufactured in a simple manner, said gate region comprising a very short vertical part (,A) of, for example, polycrystalline silicon and an overlying wider horizontal part of, for example, aluminium. Such a transistor has excellent high-frequency properties. In a preferred embodiment, the stepped portion (,) is formed by providing the insulating layer with a recess (,) whose side walls are situated above the source region (,) and the channel region (,). In a particularly simple variant, a “parasitic” gate region (,) is subsequently formed above the source region (,), which is not objectionable. The recess (,) can further be used in the formation of LDMOST whose source region (,) can be provided with an extension (,A).