Patent ID: 7069525

Claim:
A method for determining characteristics of metal oxide semiconductor (MOS) devices, the method comprising the steps of: providing a plurality of ring oscillators, the plurality of ring oscillators located within a predetermined distance of one another, each ring oscillator comprising a plurality of coupled stages, wherein: each of the plurality of coupled stages for a first given ring oscillator comprises an inverter having at least one first MOS device having a first designed gate length; each of the plurality of coupled stages for a second given ring oscillator comprises an inverter substantially identical to the inverters in the coupled stages of the first given ring oscillator and coupled to at least one second MOS device having a second designed gate length; each of the plurality of coupled stages for a third given ring oscillator comprises an inverter substantially identical to the inverters in the coupled stages of the first given ring oscillator and coupled to at least one third MOS device having a third designed gate length; the second and third designed gate lengths are different; and one of the second and third designed gate lengths is substantially equal to the first designed gate length; determining performance by using at least one of the given ring oscillators; and determining, using the plurality of ring oscillators, at least one additional characteristic of MOS devices in the plurality of ring oscillators.