Method for forming semiconductor device and semiconductor device

The invention provides a method for forming a semiconductor device and a semiconductor device. In one embodiment, the method for forming the semiconductor device includes forming a first transistor and a second transistor over a first substrate; forming a front side interconnection structure above the first transistor and the second transistor; etching at least one back side of the first substrate to expose the first transistor and the second transistor; forming a first backside through hole electrically connected to the first transistor; forming a second backside through hole electrically connected to the second transistor; depositing a dielectric layer over the first backside through hole and the second backside through hole; forming a first conductive wire in the dielectric layer, the first conductive wire being a power rail electrically connected to the first transistor through hole the first backside via; and forming a second conductive wiring in the dielectric layer, wherein the second conductive wiring