We present device simulations based on a generalized tunneling theory. The theory is compatible with standard coherent tunneling approaches and significantly increases the variety of devices that can be simulated. Quasi-bound and continuum states in the leads are treated on the same footing. Quantum charge self-consistency is included in the leads and the central device region. We compare the simulated I–V characteristics with the experimental I–V characteristics for two complex quantum device structures and find good agreement.