Methods of changing threshold voltages of semiconductor transistors by ion implantation

摘要

A method for forming a semiconductor structure. The method includes providing a semiconductor structure including a semiconductor substrate. The semiconductor substrate includes (i) a top substrate surface which defines a reference direction perpendicular to the top substrate surface and (ii) a semiconductor body region. The method further includes implanting an adjustment dose of dopants of a first doping polarity into the semiconductor body region by an adjustment implantation process. Ion bombardment of the adjustment implantation process is in the reference direction. The method further includes (i) patterning the semiconductor substrate resulting in side walls of the semiconductor body region being exposed to a surrounding ambient and then (ii) implanting a base dose of dopants of a second doping polarity into the semiconductor body region by a base implantation process. Ion bombardment of the base implantation process is in a direction which makes a non-zero angle with the reference direction.