The invention provides a method for improving the uniformity of devices. The method is applied to situations in which thin films are formed at the back surfaces of the wafers after various kinds of furnace tube techniques and are not removed by a subsequent cleaning technique or/or side walls exist at two sides of a grid electrode after the technique procedures of semiconductor devices are finished. According to the method of the invention, the thickness of silicon nitride at the back surface of each wafer is measured after source electrode and drain electrode ion implantation is completed and before high-temperature rapid thermal annealing; calculation is performed based on the thickness and the heat absorption capacity of a corresponding wafer, so that thermal annealing temperature suitable for the wafer can be determined dynamically; and an automatic control system automatically selects an annealing technique condition of a specific temperature according to the thermal annealing temperature, so that heat absorption deviation caused by too large or too small thickness of the silicon nitride at the back surfaces of the wafers can be eliminated, and therefore, device performance of different waters can tend to be consistent.