(Received November 28, 1984)
Electron acoustic images, EAIs, by electron-acoustic microscopy were studied by in situ observation at the same area of a Si transistor-chip Tr-chip under several bias conditions applied between the collector and the emitter. The results confirmed that the EAI contrast varies depending not only on the difference in the materials and the flatness of the surface but also on the bias conditions. Dislocation lines were clearly observed at the base region of the Tr-chip and were induced by the thermal diffusion process of the base layer production. However, dislocation lines were not observed from the structually same emitter region.