A plurality of gate structures are formed on a substrate. Each of the gate structures includes a first gate electrode and source and drain regions. The first gate electrode is removed from each of the gate structures. A first photoresist is applied to block gate structures having source regions in a source-down direction. A first halo implantation is performed in gate structures having source regions in a source-up direction at a first angle. The first photoresist is removed. A second photoresist is applied to block gate structures having source regions in a source-up direction. A second halo implantation is performed in gate structures having source regions in a source-down direction at a second angle. The second photoresist is removed. Replacement gate electrodes are formed in each of the gate structures.