A semiconductor device having a recessed active edge is provided. The semiconductor devices include an isolation layer disposed in a substrate to define an active region. A gate electrode is disposed to cross over the active region. A source region and a drain region are disposed in the active region on both sides of the gate electrode. A recessed region is disposed under the gate electrode and on an edge of the active region adjacent to the isolation layer. A bottom of the recessed region may be sloped down toward the isolation layer. The gate electrode may further extend into and fill the recessed region. That is, a gate extension may be disposed in the recessed region. A method of fabricating the semiconductor device is also provided.