The structures of the interface regions between CdTe crystal and electrodes in diode-type CdTe x-ray detectors with a layout of In(anode)/CdTe/Pt(cathode) are reported. The structures have been investigated by field emission scanning electron microscopy and energy-dispersive x-ray microanalysis. The investigation has revealed that the structures are complicated. The anode-side interface is a contact between In1-xTex alloys and CdTe crystal. The cathode side is a structure of Pt/(Te-rich phase)/CdTe. These findings suggest that the complicated structures in the interface regions are a possible cause for the polarization phenomenon observed in the diode-type CdTe detectors.