Semiconductor devices having nitrided gate insulating layer and methods of fabricating the same

A method of fabricating a semiconductor device, the method comprising:

• mounting a wafer on a support chuck disposed in a lower region of a chamber, wherein the wafer includes a gate trench formed in a silicon substrate, and a preliminary gate insulating layer formed on a bottom surface and inner walls of the gate trench;
• supplying microwaves from above the chamber into a central region of the chamber;
• supplying nitrogen (N2)-containing gases into the chamber to generate plasma;
• applying a radio-frequency (RF) signal having a frequency of about 13.56 MHz and power between about 100 W and about 300 W to a bias electrode disposed under the support chuck;
• and
• processing the wafer using the plasma by nitriding the preliminary gate insulating layer to form a gate insulating layer including silicon oxynitride.

A method of fabricating a semiconductor device, the method comprising:

• providing a substrate having active regions each delimited by device isolation regions, the active regions being exposed;
• forming at least one gate trench in each of the active regions;
• conformally forming a preliminary gate insulating layer including an oxide over the active region in the at least one gate trench;
• nitriding the preliminary gate insulating layer by applying a radio-frequency (RF) bias at a frequency of about 13.56 MHz with power between about 100 W and about 300 W to form a nitrided preliminary gate insulating layer including an oxynitride;
• forming a nitrided gate insulating layer and a gate electrode layer partially filling in the at least one gate trench by removing portions of the nitrided preliminary gate insulating layer and a gate electrode layer on the nitrided preliminary gate insulating layer;
• and
• forming a gate capping layer filling in a remaining portion of the at least one gate trench.