Semiconductor device including trench isolation structure and a method of manufacturing thereof

摘要

In a trench isolation structure having active regions at a main surface of a silicon substrate isolated by providing a gate electrode on an insulation film formed in a trench with a gate oxide film thereunder, the insulation film has a vertical cross section configuration wherein the carrier concentration of the active region at the proximity of the upper edge corner of the trench becomes lower than the carrier concentration at the center of the active region in a state where a predetermined bias voltage is applied to the gate electrode. According to this structure, electric field concentration at the edge of the trench isolation can be relaxed and generation of an inverse narrow channel effect suppressed. Therefore, the subthreshold characteristics can be improved.