To increase the efficiency of electronic devices their structures are getting smaller and the layered constructions are getting more complex. The inspection of these small and thin structures gives new demands on the NDT, especially in lateral and depth resolution. High-end X-ray tomography is one inspection method, which allows to detect cracks or delaminations. However, it is time consuming. Ultrasonic techniques are able to detect cracks, delaminations, and other inhomogeneities, too. Acoustic microscopy is the high-end application of ultrasonic techniques. Using frequencies between 1 MHz and 1000 MHz (1 GHz) it is possible to detect defects even in the submicron-range. In combination with scanning units with a resolution of 0.1 µm, modified transducers and special software microstructures of layered electronic devices can be inspected very fast. This method will be presented at several examples of semiconductor devices. It will be shown, that inline-inspection with acoustic microscopy is possible.