A method for forming a tunneling field effect transistor is disclosed, which includes the following steps. First, a semiconductor substrate is provided. A source region is formed on the semiconductor substrate. A tunneling region having a sidewall and a top surface is formed on the source region. A drain region is formed on the tunneling region. A gate dielectric layer is then formed, covering the sidewall and the top surface of the tunneling region. A first metal layer is formed, covering the gate dielectric layer. Subsequently, an anisotropic etching process is performed to remove a portion of the first metal layer. After the anisotropic etching process, a second metal layer is fabricated to cover the remaining first metal layer and the gate dielectric layer.