A method of forming a semiconductor device having an offset spacer may include forming a gate electrode on a semiconductor substrate. An etch stop layer including a nitride may be formed on the entire surface of the semiconductor substrate having the gate electrode. First spacers may be formed on the sidewalls of the gate electrode. The first spacers may be formed of a material layer having an etch selectivity with respect to the etch stop layer. The etch stop layer may be exposed on the semiconductor substrate on both sides of the gate electrode. Lightly-doped drain (LDD) regions may be formed in the semiconductor substrate using the gate electrode and the first spacers as an ion implantation mask. Second spacers may be formed on the first spacers. Accordingly, a semiconductor device having an offset spacer may be provided.