Methods for manufacturing a field-effect semiconductor device

A method of fabricating a field-effect transistor, comprising:

• forming on a substrate a channel layer comprising germanium;
• patterning a sacrificial gate layer comprising silicon on the channel layer;
• exposing sidewalls of the patterned sacrificial gate layer to a solution to form thereon sacrificial sidewall spacers comprising chemical silicon oxide;
• forming an elevated source and an elevated drain on exposed surfaces of the channel layer laterally adjacent the patterned sacrificial gate layer;
• after forming the elevated source and drain, forming permanent sidewall spacers on the sacrificial sidewall spacers;
• removing the sacrificial gate layer and the sacrificial sidewall spacers, thereby forming a cavity comprising an exposed channel surface and exposed inner surfaces of the permanent sidewall spacers;
• and
• depositing a permanent gate dielectric layer on the exposed channel surface of the cavity and depositing a permanent gate metal on the permanent gate dielectric layer.