Semiconductor structures are formed using diffusion topography engineering
(DTE). A preferred method includes providing a semiconductor substrate,
forming trench isolation regions that define a diffusion region,
performing a DTE in a hydrogen-containing ambient on the semiconductor
substrate, and forming a MOS device in the diffusion region. The DTE
causes silicon migration, forming a rounded or a T-shaped surface of the
diffusion regions. The method may further include recessing a portion of
the diffusion region before performing the DTE. The diffusion region has
a slanted surface after performing the DTE.