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Tunneling transistors that incorporate in the gated source an elevated p+ Si0.6Ge0.4/n- Si heterojunction and a HfO2/WN gate stack are constructed. XTEM images show in tact epitaxial SiGe with sub-10-nm thickness. The current/voltage characteristics within 77 K-300 K show behavior consistent with gate-controlled tunneling over several decades of current. Simulations using a nonlocal tunneling model support a tunneling process that occurs across the heterojunction. There is sufficient gate modulation of the surface potential at the p+ SiGe/gate-insulator interface to provide the band overlap and band bending for band-to-band tunneling (BTBT). The transfer and output characteristics are considerably improved over previous devices that used buried SiGe films, ion-implanted junctions, and SiO2 di-electrics, resulting in a reduced minimum subthreshold slope and an increased current drive with identical biasing. Also, due to the asymmetry in this structure and suppression of drain BTBT, Ion/Ioff >; 105 is achieved with Vdd = 2.5 V.