A technology is capable of simplifying a process of manufacturing an asymmetric device in forming a Tunneling Field Effect Transistor (TFET) structure. A method for manufacturing a semiconductor device comprises forming a conductive pattern over a semiconductor substrate, implanting impurity ions with the conductive pattern as a mask to form a first junction region in the semiconductor substrate, forming a first insulating film planarized with the conductive pattern over the first junction region, etching the top of the conductive pattern to expose a sidewall of the first insulating film, forming a spacer at the sidewall of the first insulating film disposed over the conductive pattern, etching the conductive pattern with the spacer as an etching mask to form a gate pattern, and forming a second junction region in the semiconductor substrate with the gate pattern as a mask.