Gate dielectric
The thin insulating film between the gate electrode and the channel of a MOS transistor. The gate's voltage acts through this film to open and close the channel.
The thinner the film, the more strongly the gate voltage acts on the channel, and the smaller the transistor can be. Silicon dioxide served for decades, but when scaling brought its thickness down to a few atoms, about one nanometre, electrons began slipping straight through and current leaked.
In 2007, at the 45-nanometre generation, Intel replaced the film with a hafnium-based material[1]. Because it transmits the voltage more effectively, that is, it has a higher dielectric constant, it can be made physically thicker while having the same effect, and leakage falls sharply. High-k refers to that high dielectric constant. In gate-all-around transistors, laying this film thinly and evenly all the way round the channel is one of the hardest steps in manufacturing.
Related terms
- MOS transistorA transistor built from a metal electrode, an oxide layer and a semiconductor, in which a voltage on the electrode alone opens and closes the channel. Most of today's chips are made of these.
- Oxide layerThe thin, glass-like film of silicon dioxide that forms on silicon when it is heated. Impervious to impurities and electrically insulating, it became the foundation of chip manufacturing.
- Gate-all-aroundA transistor structure in which the channel is a stack of thin sheets (nanosheets), each fully surrounded by the gate on all sides.