Silicon germanium film formation method and structure

Epitaxial deposition of silicon germanium in a semiconductor device is achieved without using masks. Nucleation delays induced by interactions with dopants present before deposition of the silicon germanium are used to determine a period over which an exposed substrate surface may be subjected to epitaxial deposition to form a layer of SiGe on desired parts with substantially no deposition on other parts. Dopant concentration may be changed to achieve desired thicknesses within preferred deposition times. Resulting deposited SiGe is substantially devoid of growth edge effects.