Structure and method for sram finfet device

A method of fabricating a semiconductor device, comprising:

• forming a semiconductor fin structure, the semiconductor fin structure including a bottom segment containing a first semiconductor material, a middle segment containing a second semiconductor material disposed over the bottom segment, and a top segment containing a third semiconductor material disposed over the middle segment, wherein the third semiconductor material is different from the second semiconductor material;
• converting, via a thermal oxidation process, the second semiconductor material of the middle segment into a dielectric material;
• transforming, via an annealing process, the third semiconductor layer of at least a portion of the top segment into a fourth semiconductor material;
• thereafter forming a dummy gate to wrap around the top segment;
• removing a portion of the fourth semiconductor material;
• forming, via an epitaxial growth process, source/drain regions on an un-removed portion of the fourth semiconductor material and on opposite sides of the dummy gate, wherein the un-removed portion of the fourth semiconductor material serves as a seeding layer during the epitaxial growth process;
• and
• replacing, after the source/drain regions have been formed, the dummy gate with a high-k metal gate.

A method, comprising:

• forming a fin structure over a substrate;
• the fin structure including:
• a first semiconductor material layer as its bottom portion;
• a semiconductor oxide layer as its middle portion;
• and
• a third epitaxial semiconductor material layer as its upper portion;
• depositing germanium-containing semiconductor material layer over the fin structure;
• depositing an oxide layer over the germanium-containing semiconductor material layer;
• applying a high temperature annealing to condense germanium (Ge) in a center section of the upper portion and semiconductor oxide in an outer portion of the upper portion of the fin structure;
• and
• removing the semiconductor oxide of the outer portion of the upper portion of the fin structure.