The disclosure provides a semiconductor device having a separate active region and a method of fabricating the same. The semiconductor device includes a substrate, a plurality of isolation islands, a source region, and a drain region. The substrate includes a first active region, a second active region, and a plurality of separate active regions. The separate active regions are connected to the first active region and the second active region. The separate active regions and the isolation islands are alternately disposed. The gate structure includes a body portion and a plurality of extensions. The body portion disposed on a portion of the first active region. The extensions are coupled to the body portion and extend from the body portion to the isolation islands. The source region and the drain region are respectively located in the substrate in the first active region and the second active region.