Provided is a MOSFET with an ultra short channel length and a method of fabricating the same. The ultra short channel MOSFET has a silicon wire channel region with a three-dimensional structure, and a source/drain junction formed in a silicon conductive layer formed of both sides of the silicon wire channel region. Also, a gate electrode formed on the upper surface of the silicon wire channel region by interposing a gate insulating layer having a high dielectric constant therebetween, and source and drain electrodes connected to the source/drain junction are included. The silicon wire channel region is formed with a triangular or trapezoidal section by taking advantage of different etch rates that depend on the planar orientation of the silicon. The source/drain junction is formed by a solid-state diffusion method.