METHODS OF FABRICATING SEMICONDUCTOR DEVICES AND METHODS OF FABRICATING GATE INSULATING LAYERS

A method of fabricating a semiconductor device may include forming active and field regions in a substrate; forming a gate trench in which the active and field regions are exposed; forming a gate insulating layer on a surface of the exposed active region, wherein forming the gate insulating layer includes forming a first gate oxide layer by primarily oxidizing the surface of the active region, and forming a second gate oxide layer between the surface of the active region and the first gate oxide layer by secondarily oxidizing the surface of the active region; conformally forming a gate barrier layer on the gate insulating layer and the exposed field region; forming a gate electrode layer on the gate barrier layer; and forming a gate capping layer in contact with the gate insulating layer, the gate barrier layer, and the gate electrode layer in the gate trench.