Deep isolation trench structure and deep trench capacitor on a semiconductor-on-insulator substrate

Abstract

Two trenches having different widths are formed in a semiconductor-on-insulator (SOI) substrate. An oxygen-impermeable layer and a fill material layer are formed in the trenches. The fill material layer and the oxygen-impermeable layer are removed from within a first trench. A thermal oxidation is performed to convert semiconductor materials underneath sidewalls of the first trench into an upper thermal oxide portion and a lower thermal oxide portion, while the remaining oxygen-impermeable layer on sidewalls of a second trench prevents oxidation of the semiconductor materials. After formation of a node dielectric on sidewalls of the second trench, a conductive material is deposited to fill the trenches, thereby forming a conductive trench fill portion and an inner electrode, respectively. The upper and lower thermal oxide portions function as components of dielectric material portions that electrically isolate two device regions.