Present embodiments provide for a FinFET and fabrication method thereof. The fabrication method includes two selective etching processes to form the channel. The FinFET includes a substrate, a shallow trench isolation (STI) layer, a buffer layer, an III-V group material, a high-K dielectric layer and a conductor material. The STI is formed on the substrate with a trench. The buffer layer is formed on the substrate in the trench. The III-V group material is formed on the buffer layer in vertical stacked bowl shape. The high-K dielectric layer is formed on the STI layer and surrounding the III-V group material. The conductor material is formed surrounding the high-K dielectric layer as a gate electrode.