Semiconductor device with silicon substrate with sunken oxide layer - mfd. by forming oxide interlayer, overcoating with silicon nitride, etching, isotropic etching of oxide layer and applying nitride layer

摘要

A process for prodn. of a semiconductor device with a substrate region of mono-crystalline silicon contg. an oxide pattern let into the substrate region, comprises (i) applying to one surface of the substrate a thin interlayer of Si oxide followed by a first Si nitride layer, (ii) etching the Si nitride layer in a desired pattern, (iii) removing the exposed areas of the interlayer by isotropic etching so that the parts of the underlayer lying under the edge of the first Si nitride layer are also removed, (iv) applying a second, thinner layer of Si nitride overall so that the cavity left by removing the interlayer from under the edge of the first Si nitride layer is also filled with Si nitride, and (v) removing the second Si nitride layer by etching until only the part bordering the interlayer remains together with the part filling the cavity under the edge of the first Si nitride layer.