Structures and methods for precision trench formation are disclosed. In one embodiment, a method for manufacturing a semiconductor device comprises forming a first oxygen-containing region in a semiconductor substrate by performing an oxygen ion implantation to a portion of the semiconductor substrate, and oxidizing the first oxygen-containing region using oxygen contained therein by performing a thermal processing to the semiconductor substrate, where the first oxygen-containing region is converted to a first oxide region. The method further comprises forming a groove in the semiconductor substrate by eliminating the first oxide region, where the performing thermal processing comprises subjecting the first oxygen-containing region to a gas low on oxygen.