The capacitance of a Schottky barrier diode measured as a function of reverse voltage yields the dope concentration and eventually the thickness of an epitaxially grown silicon layer. It is shown that mercury can be used as the metal contact to the silicon. This allows for a rapid and nondestructive C‒V measurement, particularly when combined with an automated instrument. The results obtained with different surface treatments are discussed. For reliable and reproducible results N‐type silicon should be covered with a thin oxide layer about 50Aå thick, which can easily be made wet chemically. The precision which can be attained with this system in actual practice amounts to ±2% or better and the accuracy depends on the definition of thickness used. This technique with the mercury contacting accessory works equally well on and