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The postmetallization annealing (PMA) effect was investigated for a TiN-gate Ge metal-oxide-semiconductor capacitor with an ultrathin SiO2/GeO2 bilayer passivation. PMA at 450 °C led to the incorporation of nitrogen atoms into the gate stack. Consequently, the flat band voltage shifted from −0.79 to +0.23 V, resulting from a decrease in the dipole at the SiO2/GeO2 interface and the accompanying creation of a negative charge. The hysteresis decreased from 98 to 27 mV and the interface state density decreased from 6×1011 to 2.5×1011 cm−2 eV−1, as results of the nitrogen termination of defects at the SiO2/GeO2 interface and/or in the GeO2 interlayer.

Metal/Ge contacts with high Schottky barrier heights on p- and n-Ge substrates could be formed using direct sputter depositions from TiN and Hf, respectively. The barrier heights were 0.53 and 0.60 eV for the p- and n-Ge substrates, respectively, which are available to source/drains (S/Ds) in Schottky n- and p-channel metal–oxide–semiconductor field-effect transistors (MOSFETs). We fabricated the n- and p-MOSFETs and demonstrated their operation. In particular, the n-MOSFET operation is the first demonstration of S/D using directly contacted metal/Ge. This work opens a method for embodying Schottky S/D Ge complementary MOS devices.

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