Abstract: A Metal Oxide Semiconductor (MOS) transistor comprising: a source; a gate; and a drain, the source, gate and drain being located in or on a well structure of a first doping polarity located in or on a substrate; wherein at least one of the source and the drain comprises a first structure comprising: a first region forming a first drift region, the first region being of a second doping polarity opposite the first doping polarity; a second region of the second doping polarity in or on the first region, the second region being a well region and having a doping concentration which is higher than the doping concentration of the first region; and a third region of the second doping polarity in or on the second region. Due to the presence of the second region the transistor may have a lower ON resistance when compared with a similar transistor which does not have the second region. The breakdown voltage may be influenced only to a small extent.

Abstract: A high voltage metal oxide semiconductor (HVMOS) transistor (1) comprises a drift region (8) comprising a material having a mobility which is higher than a mobility of Si. There is also provided a method of manufacturing said transistor, the method comprising forming a drift region comprising a material having a mobility which is higher than a mobility of Silicon. The material can be a Si—Ge strained material. The on- resistance is reduced compared to a transistor with a drift region made of Si, so that the trade-off between breakdown voltage and on-resistance is improved.

Abstract: A Metal Oxide Semiconductor (MOS) transistor comprising: a source; a gate; and a drain, the source, gate and drain being located in or on a well structure of a first doping polarity located in or on a substrate; wherein at least one of the source and the drain comprises a first structure comprising: a first region forming a first drift region, the first region being of a second doping polarity opposite the first doping polarity; a second region of the second doping polarity in or on the first region, the second region being a well region and having a doping concentration which is higher than the doping concentration of the first region; and a third region of the second doping polarity in or on the second region. Due to the presence of the second region the transistor may have a lower ON resistance when compared with a similar transistor which does not have the second region. The breakdown voltage may be influenced only to a small extent.