Formation of notched gate using a multi-layer stack

摘要

A field effect transistor device has a semiconductor substrate having a predetermined impurity concentration of a first conductivity type. Inpurity layers of a second conductivity type are formed spaced apart at the main surface of the semiconductor substrate. The impurity layers make up source/drain regions. A region between the impurity layers defines a channel region. A notch-shaped conductive layer is formed on the channel region. The notch-shaped conductive layer has an upper layer section longer than a lower layer section. The upper and lower layer sections are formed of at least two different materials, one being silicon-germanium layer with varying germanium content. The material of the lower layer section can be etched at a greater rate than the material of the upper layer section during a common etching process.