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We have performed a simulation study of symmetric ultrathin-body double-gate (SUTBDG) devices with metal source/drain (S/D) structures designed for low-operating-power applications. A relatively high S/D Schottky barrier strongly influences the threshold voltages of the devices. The drive current (ION) is dominated by barrier tunneling for nonnegative SBHs. Both electrons and holes may contribute to the off-state current (IOFF). Tunneling from the drain terminal limits the minimum obtainable IOFF. Germanium channel devices with metal S/D and a given IOFF have smaller ION than similar silicon devices. With low nonnegative Schottky barrier heights (SBHs), metal S/D devices can outperform doped S/D devices, if the device performance degradation due to series resistances and parasitic capacitances is taken into account. Based on realistic device design rules, we have determined the upper bounds of S/D SBHs that allow metal S/D devices to offer improved performance over doped S/D devices with different body thicknesses.