A semiconductor device and fabrication method thereof are disclosed. An example semiconductor device includes a semiconductor substrate having a device isolation area defining an active area; a gate oxide layer formed on the active area of the substrate; a gate on the gate oxide layer; a spacer provided to a sidewall of the gate; and a well region provided within the active area. The well region includes a threshold voltage adjustment doped region, a halo region, a source region, a drain region, an additional doped region, and a channel stop region, the additional doped region provided between the well region and each of the source and drain regions.