of the filter circuits by the subsequent trimming step as explained fig4 shows the frequency distribution of a multitude of measured filters produced on a wafer in a histogram the left hand distribution shows the measured frequencies on the wafer after deposition of a trimming layer of silicon oxide this distribution is called the initial distribution the right hand distribution shows the measured frequencies on the same wafer after the trimming process according to the inventive method the right hand distribution is called the final distribution after the deposition of a trimming layer the mean frequency measured on the wafer is intentionally too low for the desired product during the trimming process the frequencies are respectively shifted towards the goal frequency as this process is controlled in the area according to the measured initial distribution and the initial deviation from the goal frequency calculated therefrom the final distribution resulting from the process is much smaller the measured final frequencies are within a smaller range in this embodiment the standard deviation 1 u03c3 is about 3800 ppm for the initial distribution by the trimming process the standard deviation 1 u03c3 has been reduced to about 600 ppm this makes the frequencies of at least 90 of the filters lie within an allowed tolerance thus these 90 of the filters are correctly working filters another embodiment or another allowed tolerance may still improve this yield moreover the scope of the present application is not intended to be limited to the particular embodiments of the process machine manufacture composition of matter means methods and steps described in the specification as one of ordinary skill in the art will readily appreciate from the disclosure of the present invention processes machines manufacture compositions of.