"28HP is the first process from TSMC to use High-k Metal Gate (HKMG)technology, as opposed to the typical silicon oxynitride (SiON) found in 40nm GPUs. HKMG uses a material with a high dielectric constant instead of the traditional silicon dioxide gate dielectric. This allows for a substantial reduction in gate leakage, thus lowering overall power consumption and allowing for higher clock speeds.
According to sources within TSMC, the 28HP HKMG process is doing very well. So well, in fact, that it supports up to a 45 percent clock speed improvement over the firm's own 40G process used to make the last two generations of video cards. This speed improvement is based on the same leakage per gate, but the GPU firms may choose to favor lower power consumption over a pure speed boost."
