It is an object of the present invention to provide a nonvolatile memory device, in which additional writing is possible other than in manufacturing and forgery and the like due to rewriting can be prevented, and a semiconductor device having the memory device. It is another object of the present invention to provide an inexpensive and nonvolatile memory device with high reliability and a semiconductor device. According to one feature of the present invention, a memory device includes a first conductive layer formed over an insulating surface, a second conductive layer, a first insulating layer interposed between the first conductive layer and the second conductive layer, and a second insulating layer which covers a part of the first conductive layer, wherein the first insulating layer covers an edge portion of the first conductive layer, the insulating surface, and the second insulating layer.