In this work we present a comprehensive comparison of ultra thin thermally nitrided (TN) to plasma nitrided (PN) gate dielectrics (GD). We will show that thermal nitridation is a promising technique to increase the nitrogen concentration up to 25%. Furthermore, we will demonstrate that ultra thin thermally nitrided GD have the potential to be an alternative solution compared to plasma nitrided GD. This work includes the analysis of physical and electrical parameters as well as reliability results from reliability characterization. Additionally, we investigated the impact of Deuterium on electrical parameters and reliability behavior.