According to the invention there is a method of etching a semiconductor substrate to reveal one or more features buried in the substrate, the method including the steps of:
performing a first etch step using a plasma in which a bias power is applied to the substrate to produce an electrical bias;
performing a second etch step without a bias power or with a bias power which is lower than the bias power applied during the first etch step; and
alternately repeating the first and second etch steps.
