An object is to provide an antifuse with little power consumption at the time of writing. The antifuse is used for a memory element in a read-only memory device. The antifuse includes a first conductive layer, a multilayer film of two or more layers in which an amorphous silicon film and an insulating film are alternately stacked over the first conductive layer, and a second conductive layer over the multilayer film. Voltage is applied between the first and second conductive layers and resistance of the multilayer film is decreased, whereby data is written to the memory element. When an insulating film having higher resistance than amorphous silicon is formed between the first and second conductive layers, current flowing through the antifuse at the time of writing is reduced.