This paper focuses on doping type and doping level characterization of silicon-on-insulator wafers prior to device fabrication. The ability of the point-contact pseudo-metar-oxide-semiconductor transistor to analyze background doping is investigated thoroughly both theoretically and through a comparison with secondary ion mass spectroscopy on intentionally doped wafers. A new method using mercury contacts is proposed to determine the semiconductor type for extremely low doping levels. No sample preparation is needed and unambiguous results are obtained. The physical basis of the measurement is investigated and the method is demonstrated on bulk and silicon-on-insulator wafers.