Polycrystalline silicon is also known as "semicrystalline silicon", "polysilicon", "poly-Si", or just "poly". Comparing with single-crystal silicon, polycrystalline silicon always has visible grain, as it is composed of small silicon crystals. The purity of polysilicon can be up to 99.9999%, after depositing with high technologies. Polysilicon thin films can be widely used as MOS transistor gate electrodes and for interconnection in MOS circuits. The electrical feature of a poly-Si thin film depends on its doping. Usually, more dopants result in lower resistivity, but the grain boundaries are the most barriers for poly-Si's conductivity. Semicrystalline silicon is sometimes used as resistor, as well as for ensuring ohmic contacts for shallow junctions.