One method of forming a semiconductor device includes forming a gate electrode on a substrate and then forming a spacer adjacent to a sidewall of the gate electrode. An active region is formed in the substrate adjacent to the spacer and spaced apart from the gate electrode using a first dopant material of a first conductivity type. A protecting layer is formed over the active region and adjacent to the spacer. At least a portion of the spacer is then removed to form an opening between the protecting layer and the gate electrode. In some instances, the spacer may be formed by independent deposition of two different materials (e.g., silicon nitride and silicon dioxide), one of which can be selectively removed with respect to the other. A lightly-doped region is formed in the substrate adjacent to the gate electrode using a second dopant material of the first conductivity type. This lightly-doped region may be formed, for example, prior to formation of the spacer, between the formation of two portions of the spacer, or after removing at least a portion of the spacer. A halo region is formed through the opening resulting from removing a portion of the spacer. The halo region is deeper in the substrate than the lightly-doped region and is adjacent to the active region. The halo region is formed using a third dopant material of a conductivity type different than the first conductivity type.