[en] Following previous work in particle physics, the MPI Semiconductor Laboratory has been founded with the purpose of developing novel semiconductor detectors for particle physics and X-ray astronomy. A short description of the already successfully concluded development of pn-CCDs for focal imaging in X-ray astronomy (XMM/Newton X-ray Observatory) is given and the much more demanding requirements in a future X-ray astronomy experiment (XEUS) are discussed. A new type of pixel detector is proposed which will be capable to meet these requirements. It is based on the 'DEPleted-Field Effect Transistor (DEPFET)' principle. The device operated on a fully depleted silicon wafer allows an internal charge amplification directly above the position where the signal conversion takes place. A very low gate capacitance of the DEPMOS transistor leads to low noise amplification. In contrast to CCDs, neither transfer loss nor 'out-of-time events' can occur in a DEPFET-array. A very interesting feature is the possibility of repeated non-destructive readout which can be used for noise reduction even for the low-frequency (1/f) noise. This type of detector will also have its applications in linear collider experiments