Metal oxide semiconductor and method of making the same

摘要

A metal oxide semiconductor transistor including a silicon substrate of a first conductivity type and having a central portion having a channel region which has a recessed surface. The substrate has another portion which has a flat surface. A thin gate oxide film is formed on the recessed surface and an oxide film, which is thicker than the gate oxide film, is formed on the flat surface. A gate is formed on the gate oxide film and has a flat upper surface and a convex lower surface. A thick cap oxide film is formed on the gate. Low concentration source and drain regions of a second conductivity type overlap completely with the gate and are formed adjacent to the channel region. High concentration source and drain regions of the second conductivity type are formed on the flat surface of the silicon substrate and adjacent to the low concentration source and drain regions. Impurity regions are either formed on the silicon substrate and enclose the low concentration source and drain regions, or are of the first conductivity type and positioned in the bulk and under the channel region.