from fig5 we see that this severely limits the range of geometries that can be considered excluding all those geometries that are optimally insensitive to u03b4 variations fig3 from the analysis set out above it had previously been understood by persons skilled in the art that no single optimal geometry for a mems resonator existed which could benefit from insensitivity to both u03b4 and t ox by means of the present invention it is possible to design a mems resonator that is simultaneously temperature compensated and optimally insensitive to both u03b4 and t ox variations this is achieved through design of the geometry of the resonator by means of the present invention the optimum geometries for insensitivity to t ox and etch u03b4 variations are independently tuneable by for example patterning the resonator such that the supply of silicon for oxidation is limited or the space into which the grown oxide needs to expand is limited it is therefore possible to enhance the sensitivity of the mass region to u03b4 variations without impacting or even reducing the sensitivity of the mass to t ox variations and to thereby realise a single geometry that is simultaneously first order insensitive to both variations.