The present application provides a method for improving the metal work function boundary effect in FinFET process, the method comprises steps of: depositing a first TiN layer on four fin structures. The first TiN layer has no gap between the second and the third fin structures; removing the first TiN layer up to a first distance from the midline between the second and third fin structures at the second fin structure side; depositing a second TiN layer; removing the second and first TiN layers from second fin structure. The thickness of the TiN layer at the bottom edge of the fin structure at the later structure of the ultra-low threshold voltage P-type transistor will be smaller from this process. Thus formed TiN layer is less prone to a bottom undercut during etching, thereby reducing the metal boundary effect and increasing of the threshold voltage of the device.