A method of forming diffusion sidewalls in a semiconductor structure and a semiconductor structure having diffusion sidewalls includes etching a trench into a semiconductor substrate to form first and second active regions, lining each trench with an oxide liner along exposed sidewalls of an active silicon region (RX) of the first and second active regions, removing the oxide liner formed along the exposed sidewalls of the RX region of one of the first and second active regions, forming diffusion sidewalls by epitaxially growing in-situ doped material within the exposed sidewalls of the RX region of the one of the first and second active regions, and forming an isolation region within the trench between the first and second active regions to electrically isolate the first and second active regions from each other.