Non-uniformity in electric field causes early onset of tunneling near the edge of InAs/GaSb hetero-junction tunneling field-effect transistors. When a small area, often an edge, of the tunneling junction has a lower turn-on voltage, the steep switching characteristic is degraded. Fermi pinning at InAs surface greatly worsen the uniformity. We propose a dual-metal gate structure to address the nonuniformity issue. With proper choice of work functions, the dual-metal gate structure can effectively suppress the early onset of edge tunneling and significantly improve the subthreshold swing.