Semiconductor devices with shaped cavities for embedding germanium material and manufacturing processes thereof

A semiconductor device comprising:

• a substrate comprising silicon material;
• a first cavity region positioned within the substrate, the second cavity region comprising a top portion, a middle portion, and a base portion, the top portion comprising substantially vertical sidewalls, the middle portion comprising convex sidewalls interfacing the substrate, and the base portion comprising a substantially flat bottom surface and substantially vertical sidewalls;
• and
• a filling material comprising silicon and germanium material positioned at least partially within the first cavity region.

A method for fabricating a semiconductor device, the method comprising:

• providing a substrate, the substrate consisting essentially of silicon material;
• defining a cavity region on the substrate;
• etching the substrate to form a cavity at the cavity region, the cavity comprising a top portion and a bottom portion;
• forming a layer of silicon oxide material within the bottom portion, the layer of the silicon oxide material interfacing bottom sidewalls of the substrate;
• forming a spacer on sidewalls of the top portion;
• removing the layer of silicon oxide material to expose the bottom sidewalls of the substrate;
• enlarging the bottom portion of the cavity by selectively etching the bottom sidewalls to form a first shaped cavity, the first shaped cavity comprising a convex portion interfacing with the bottom sidewalls;
• and
• filing the first cavity with a filling material, the filling material comprising silicon and germanium material.