We present the Vienna Schrödinger Poisson solver (VSP), which uses a quantum mechanical transport mode for closed as well as open boundary problems. The thereby calculated carrier concentration is used in the Poisson equation in a self-consistent manner. The band structure for electrons and holes is given by an arbitrary number of valley sorts, defined by an anisotropic effective mass and a band-edge energy. In this way a wide range of materials can be treated. Also, the effects of substrate orientation as well as strain on the band structure are taken into account. For investigations of MOS inversion layers, a closed boundary solver using a predictor corrector scheme is applied. VSP includes models for interface traps and bulk traps in arbitrarily stacked gate dielectrics. For the estimation of leakage currents, carriers in quasi-bound states (QBS) as well as free carriers are considered. Therefore, direct tunneling and trap-assisted tunneling are taken properly into account. These calculations are performed in a post-processing step, since they have a negligible influence on the electrostatic device's behavior. In addition, novel device designs, like DG-MOS structures, can be investigated. For systems which are dominated by transport phenomena, like resonant tunneling diodes (RTD), an open boundary solver using the non-equilibrium Green's function formalism is available. We use an adaptive method to generate a non-uniform mesh for the energy-space. Very narrow resonances are resolved, while the total number of grid points is kept low, thus delivering stable results at reasonable simulation times. The software is written in C++ using state-of-the-art software design techniques. Critical numerical calculations are performed with stable and powerful numerical libraries Blas, Lapack, and Arpack. VSP has a graphical user interface written in Java, as well as a text-based interface.