The metal-oxide semiconductor structure includes a substrate, a gate dielectric multi-layer, an etch stop layer, a work function metallic layer, a barrier layer and a silicide layer. The substrate has a trench. The gate dielectric multi-layer overlies the trench, in which the gate dielectric multi-layer includes a high-k capping layer with a fluorine concentration substantially in a range from 1 at % to 10 at %. The etch stop layer is disposed on the gate dielectric multi-layer. The work function metallic layer is disposed on the etch stop layer. The barrier layer is disposed on the work function metallic layer. The silicide layer is disposed on the barrier layer.