Patent ID: 8450177
Filing Date: 2013-05-28
Classification: H01L

Abstract:
1. A method for forming a field effect transistor, comprising: forming a semiconductor region of a first conductivity type having an upper surface and a lower surface, the lower surface of the semiconductor region extending over and abutting a substrate, the semiconductor region including a doped sinker region of the first conductivity type; forming a well region of a second conductivity type in the semiconductor region; forming a gate electrode over the semiconductor region; forming an upper lightly-doped drain (LDD) region of the first conductivity type in the semiconductor region; and forming a lower LDD region of the first conductivity type in the semiconductor region, the lower LDD region being disposed over and in contact with the doped sinker region, the upper LDD region being disposed over and in contact with the lower LDD region, the doped sinker region having a higher doping concentration than the lower LDD region, and the lower LDD region having a higher doping concentration than the upper LDD region.