Rational bottom-up assembly of nanowire networks may be a way to successfully continue the miniaturization, which is the main driving force behind the semiconductor industry. So far, the fabrication of branched nanowire structures is based on processes, which are limiting the control over crystalline quality, position of the junction and overall morphology. [1,2] Here we report a rational bottom-up epitaxial fabrication of planar nanowire architectures. Bottom-up growth of nanowires is the preferred route as it provides complex contact schemes, such as gates underneath and superconducting contacts on top of the structure, which cannot be easily achieved by top-down methods. Furthermore, nanowire growth grants a great degree of freedom in combining materials with different lattice parameters and doping profiles, [3,4] allowing for configurations impossible to realize in thin film geometry.