The generation velocity of the vertical sidewall of a shallow trench isolated wafer has been measured using a simple capacitance-transient technique. We found high generation velocities at the sidewall of circa 2570 cm s(-1) reduced to 1040 cm s(-1) after hydrogen annealing representative of a degraded interface caused by the dry etch process. The measurement technique is shown to be a very simple and effective evaluation tool for process test and optimisation.