Irrespective of a specification of the controller, a plurality of TFTs are formed for the controller on a substrate in advance. Then, in accordance with a design of the controller, connection is achieved among sources, drains, and gates, which serve as three terminals in each of the plural TFTs, appropriately through a wiring formed on a layer different from the one where the plural TFTs are formed, so that the controller with a desired specification is formed. At this time, it is not required to use all the TFTs arranged on the substrate and some TFTs may remain unused depending on the specification of the controller.