For optimization of the design of multiterminal silicon single piezoelements with an arbitrary layout, we have proposed a two-dimensional mathematical model based on a boundary value problem. The model takes into account the impact of external resistive circuits on the sensitivity and output voltage. This model is considered for piezoelements situated in a field of uniform mechanical stress. The accuracy of the model is proven by an agreement between the numerical simulation results, the closed-form ones and the experimental data. By simulation, the dependence of the sensitivity change on the change of the output voltage of four-terminal silicon single piezoelements due to connecting external circuits is found. The results are compared with experimental data obtained for the fabricated pressure sensors.