A semiconductor device includes a first semiconductor substrate with a first transistor therein. The first transistor includes a first source-drain formed by a doped region in the first semiconductor substrate. An intermediary insulating layer is formed on and above the first semiconductor substrate. A second semiconductor substrate is formed on and above the intermediary insulating layer. A second transistor is formed in the second semiconductor substrate, and includes a second source-drain formed by a doped region in the second semiconductor substrate. A trench is formed in the second semiconductor substrate and in contact with the doped region for the second semiconductor substrate. The trench has a thickness equal to that of the second semiconductor substrate. Metal wiring extends from a contact with the doped region for the first source-drain, through the intermediary insulating layer and the trench, to make electrical contact with the doped region for the second source-drain.