P-type buried regions 104a and 104b are formed in an extended drain region 102 formed in a P-type semiconductor substrate 110. An N-type buried region 113 is formed between the P-type buried regions 104a and 104b. An N-type impurity concentration of the N-type buried region 113 along a G G' plane is low in the vicinity of boundaries between the N-type buried region 113 and the P-type buried regions 104a and 104b and is increased from the boundaries to an inside of the N-type buried region 113.