A method of manufacturing a semiconductor device includes providing a semiconductor wafer and forming at least one first trench in the wafer having first and second sidewalls and a first orientation on the wafer. The first sidewall of the at least one first trench is implanted with a dopant of a first conductivity at a first implantation direction. The first sidewall of the at least one first trench is implanted with the dopant of the first conductivity at a second implantation direction. The second implantation direction is orthogonal to the first implantation direction. The first and second implantation directions are non-orthogonal to the first sidewall.