Methods of forming a bulk field effect transistor (fet) with sub-source/drain isolation layers and the resulting structures

Abstract

Disclosed are structures (e.g., a fin-type field effect transistor (FINFET) and a nanowire-type FET (NWFET)) and methods of forming the structures. In the methods, a fin is formed. For a FINFET, the fin includes a first semiconductor material. For an NWFET, the fin includes alternating layers of first and second semiconductor materials. A gate is formed on the fin. Recesses are formed in the fin adjacent to the gate and extend to (or into) a semiconductor layer, below, made of the second semiconductor material. An oxidation process forms oxide layers on exposed semiconductor surfaces in the recesses including a first oxide material on the first semiconductor material and a second oxide material on the second semiconductor material. The first oxide material is then selectively removed and source/drain regions are formed by lateral epitaxial deposition in the recesses. The remaining second oxide material minimizes sub-channel region source-to-drain leakage.