Ultra thin delta E-detectors for spectroscopic applications have been fabricated and characterized down to a thickness of 4.5 μm. A common one-side mask aligner was in use to fabricate the detectors. The detectors display low leakage current and the resulting capacitance is close to the detector window capacitance below a threshold voltage. The detector telescope should be slightly tilted to reduce the probability for channeling. However, even better control of the thickness uniformity is needed to improve the resolution in the E-E detector telescope