Substrate based on silicon nitride for semiconductor devices, wherein said substrate as crystalline phase of silicon nitride (Si ₃ N _4), silicon carbide (SiC) and silicon oxynitride (Si ₂ N ₂ O) and the phase component to silicon ≤ 5%, the shrinkage at the preparation of <5% and the open porosity of the substrate <15 vol .-% is as well as methods for its production.