Patent ID: 8169039
Filing Date: 2012-05-01
Classification: H01L

Abstract:
1. A semiconductor device including a supporting substrate, a buried oxide film formed on the supporting substrate, a silicon layer formed on the buried oxide film, an element separating isolation film included in the silicon layer, and an MOS transistor disposed in a region separated by the element separating isolation film, wherein the MOS transistor comprises: a first-conductivity-type low-concentration drain region; a source region; an ohmic drain region; a second-conductivity-type channel region; an ohmic channel region; a gate isolation film; and a gate electrode, wherein each of the first-conductivity-type low-concentration drain region, the source region, the ohmic drain region, the second-conductivity-type channel region, and the ohmic channel region is formed in the silicon layer so as to have a depth from a surface of the silicon layer to the buried oxide film, the gate isolation film is formed on the silicon layer so as to be formed on the second-conductivity-type channel region and the first-conductivity-type low-concentration drain region, the gate electrode is formed on the gate isolation film, the first-conductivity-type low-concentration drain region has relatively low first-conductive-type impurity concentration, the second-conductivity-type channel region has relatively low second-conductivity-type impurity concentration and is disposed adjacent to the first-conductivity-type low-concentration drain region, the source region has a first-conductive-type impurity concentration higher than that of the first-conductivity-type low-concentration drain region and is disposed adjacent to the second-conductivity-type channel region in a manner such that the source region is disposed opposite to the first-conductivity-type low-concentration drain region when viewed from the second-conductivity-type channel region, the ohmic drain region has the first-conductive-type impurity concentration higher than that of the first-conductivity-type low-concentration drain region and is disposed adjacent to the first-conductivity-type low-concentration drain region in a manner such that the ohmic drain region is disposed opposite to the second-conductivity-type channel region when viewed from the first-conductivity-type low-concentration drain region, the ohmic channel region has a second-conductive-type impurity concentration higher than that of the second-conductivity-type channel region and is disposed adjacent to the second-conductivity-type channel region, when viewed from a top, the gate electrode is formed on the second-conductivity-type channel region and a part of the first-conductivity-type low-concentration drain region adjacent to the second-conductivity-type channel region and is disposed in a manner such that the gate electrode is separated from the ohmic drain region, the second-conductivity-type channel region includes plural channel layers having different second-conductive-type impurity concentrations from each other in a manner such that the closer the channel layer is to the surface of the silicon layer, the lower the second-conductive-type impurity concentration of the channel layer becomes, and the first-conductivity-type low-concentration drain region includes plural low-concentration drain layers having different first-conductive-type impurity concentrations from each other in a manner such that the closer the low-concentration drain layer is to the surface of the silicon layer, the higher the first-conductive-type impurity concentration of the low-concentration drain layer becomes.