A high-voltage MOS transistor includes a semiconductor substrate, a gate oxide layer on the semiconductor substrate, a gate on the gate oxide layer, a spacer covering a sidewall of the gate, a source on one side of the gate, and a drain on the other side of the gate. The gate includes at least a first discrete segment and a second discrete segment. The first discrete segment is not in direct contact with the second discrete segment. The spacer fills into a gap between the first discrete segment and the second discrete segment.