It is an object to provide techniques for forming a field emission device of a field emission display device with the use of an inexpensive large-sized substrate according to the process that enables improving productivity.A field emission device according to the present invention includes a cathode electrode formed on an insulating surface of a substrate and a convex electron emission portion formed at a surface of the cathode electrode, and the cathode electrode and the electron emission portion include the same semiconductor film. The electron emission portion has a conical shape or a whiskers shape.