Device having self-aligned double gate formed by backside engineering, and device having super-steep retrograded island

摘要

A method of forming a dual gate semiconductor device is provided that includes providing a substrate having a first semiconductor layer and a second semiconductor layer, in which a first gate structure is formed on the second semiconductor layer. The second semiconductor layer and the first semiconductor layer are etched to expose the substrate using the first gate structure as an etch mask. A remaining portion of the first semiconductor layer is present underlying the first gate structure having edges aligned to the edges of the first gate structure. An epitaxial semiconductor material is formed on exposed portions of the substrate. The substrate and the remaining portion of the first semiconductor layer are removed to provide a recess having edges aligned to the edges of the first gate structure, and a second gate structure is formed in the recess. A method of forming a retrograded island is also provided.