It is expected that the leakage current can be reduced by nitridation of silicon before high-k dielectric deposition. In reality, it is not so simple because the nucleation of high-k dielectric on nitrided silicon may be different from the nucleation on silicon. In addition, the interfacial layer between the high-k dielectric becomes thinner because of the nitridation. Furthermore, the bandgap of the interfacial layer becomes smaller due to the nitridation. However, there may be less defect states in the high-k dielectric because of the nitridation. More in-depth study is needed to clarify whether leakage current is really reduced by nitridation. Experimental observation indicates the leakage current can be increased or decreased by nitridation depending on the details of the processing conditions. However, the capacitance is usually increased by nitridation; reduction of capacitance due to RTN is an unusual observation but it is possible.