Gate structure and a transistor having asymmetric spacer elements and methods of forming the same

Abstract

Methods for forming asymmetric gate structures comprising spacer elements disposed on the opposed sides of a gate electrode and having a different width are disclosed. The asymmetric gate structures are employed to form an asymmetric design of a halo region and extension regions of a field effect transistor using a symmetric implantation scheme, or to further enhance the effectiveness of asymmetric implantation schemes. The transistor performance may be significantly enhanced for a given basic transistor architecture. In particular, a large overlap area may be created at the source side with a steep concentration gradient of the PN junction due to the provision of the halo region, whereas the drain overlap may be significantly reduced or may even be completely avoided to further enhance the transistor performance.