A system and method for suppressing sub-oxide formation during the manufacturing of semiconductor devices (such as MOSFET transistor) with high-k gate dielectric is disclosed. In one example, the MOSFET transistor includes a gate structure including a high-k gate dielectric and a gate electrode. In this example, the gate structure is covered with a nitride layer that is used to prevent oxygen from entering the structure during processing, yet is sufficiently thin to be effectively transparent to the processing.