A high frequency semiconductor device including a high frequency semiconductor chip, comprising an active region provided on a front face side of the high frequency semiconductor chip; a covering electrode provided on the active region and connected to a ground potential; and a back face wiring provided on a back face side of the high frequency semiconductor chip. The back face wiring forms a high frequency transmission line together with the covering electrode functioning as a high frequency ground plate. A front face wiring may be provided on the front face side of the high frequency semiconductor chip to form a high frequency transmission line together with the covering electrode.