A disclosed semiconductor device includes an MOS transistor having an N-type low-concentration drain region, a source region, an ohmic drain region, a P-type channel region, an ohmic channel region, a gate isolation film, and a gate electrode. The N-type low-concentration drain region includes two low-concentration drain layers in which the N-type impurity concentration of the upper layer is higher than that of the lower layer; the P-type channel region includes two channel layers in which the P-type impurity concentration of the upper layer is lower than that of the lower layer; and the gate electrode is formed on the P-type channel region and the N-type low-concentration drain region and disposed to be separated from the ohmic drain region when viewed from the top.