a sheet - like miniaturized electronic device includes an electronic component assembly with a wiring base having switch contacts and a semiconductor ic chip operated by signals from the switch contacts . a display panel displays data according to signals from the semiconductor ic chip , and a battery supplies a drive voltage to the semiconductor ic chip . the wiring base , display panel and battery are electrically connected to one another and arranged in the same plane . an upper cover is provided in close contact with the upper side of the electronic component assembly , and has an operating section and a transparent display window . a lower cover is provided through an adhesive layer to the underside of the electronic component assembly .