Semiconductor devices are being developed that include great amounts of circuitry in ever-decreasing areas. Such circuitry, as measured in transistor counts and other components, increases in every product generation. Furthermore, devices are fabricated according to smaller technologies. Many of today's semiconductor devices are formed at process geometries of 130 nanometers (nm) and lower, and this trend continues as other products are introduced at ever smaller geometries.
As a result, greater amounts of functionality can be present in a single semiconductor package. The circuitry present in such a package can require significant amounts of power for its small size. For example, for a given device to achieve a desired level of performance, a relatively high power consumption can be required. By consuming higher power, the semiconductor package is subjected to high heat conditions, oftentimes in excess of 125 degrees. Such high temperatures can negatively affect reliability of the semiconductor device. At the same time, smaller process technologies enable the package to become very small, which allows less heat to be conducted away from the semiconductor device within the package. Accordingly, the amount of power that can be consumed by the semiconductor device can be limited by heat factors. Furthermore, for devices that operate on battery power, reduced power consumption enables longer operating times.
A consideration in designing integrated circuits (ICs) is process variations that occur in fabrication. That is, individual wafers of a given lot, and even individual dice on a wafer, can have varying process capabilities. Accordingly, design methodologies typically incorporate so-called process corners, which are used to simulate best case/worst case scenarios. For example, simulations can be run in design of integrated circuits to model the circuitry for fast process corners and similarly for slow process corners with respect to timing issues and so forth. Typically, circuitry is designed such that the transistors and other components are sized to meet timing and other budgets in case of a slow process corner device.
However, when actual semiconductor devices are fabricated that have a fast variation, the circuitry, especially digital circuits on the device, consumes greater power. A need thus exists to improve power dissipation in semiconductor devices.