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This paper presents modeling of manufacturing variability and body bias effect for subthreshold circuits based on measurement of a device array circuit in a 90 nm technology. The device array consists of P/NMOS transistors and ring oscillators. This work verifies the correlation between the variation model extracted from IV measurement results and oscillation frequencies, which means the transistor-level variation model is examined and confirmed in terms of circuit performance. We demonstrate that delay variations of subthreshold circuits are well characterized with two parameters - threshold voltage and subthreshold swing parameter. We reveal that body bias effect is a less statistical phenomenon and threshold voltage shift by body biasing can be modeled deterministically.