3D CMOS devices in recrystallized silicon

A 2 μm scale three-dimensional CMOS process has been developed which allows the fabrication of MOS devices in two independent active device layers. NMOS transistors have been fabricated in the substrate and CMOS devices, including inverters and ring oscillators, in a thin laser-recrystallized polysilicon layer. The processing parameters were determined carefully in order to obtain a monocrystalline top layer and to avoid any damage to the underlying devices already existing.