MOS transistor having protruded-shape channel and method of fabricating the same

A MOS transistor that has a protruding portion with a favorable vertical profile and a protruded-shape channel that requires no additional photolithography process, and a method of fabricating the same are provided. A first mask that defines an isolation region of a substrate is overall etched to form a second mask with a smaller width than the first mask. Then, the substrate is etched to a predetermined depth while using the second mask as an etch mask, thereby forming the protruding portion. Without performing a photolithography process, the protruding portion has a favorable profile and the protruding height of an isolation layer is adjusted to be capable of appropriately performing ion implantation upon the protruding portion.