CdO/Si heterojunctions were fabricated by depositing CdO polycrystalline thin films on p-type single crystalline silicon wafers by CBD. The current-voltage characteristics under dark and illumination of CdO/Si devices resemble those of a light sensitive diode. From the CdO/Si diode spectral sensitivity curves (A/W), it has been implied that CdO films allow a high sensitivity response in the visible and the near infrared regions.