1. A method of model-based measurement of semiconductor device features using a scatterometer system, the method comprising: defining a cost function depending upon a plurality of variable parameters of the scatterometer system and upon a plurality of variable parameters for computer-implemented modeling to determine measurement results; establishing constraints for the plurality of variable parameters of the scatterometer system and for the plurality of variable parameters for the computer-implemented modeling; performing a computer-implemented optimization procedure to determine an optimized global set of parameters, including both the variable parameters of the scatterometer system and the variable parameters for the computer-implemented modeling, which result in a minimal value of the cost function; and applying the optimized global set of parameters to configure the scatterometer system and the computer-implemented modeling.