A semiconductor device includes a first well region 3a; a second well region 3b; a first active region 21a surrounded by an isolation region 2; a second active region 21b surrounded by the isolation regions 2 and 2B; a first MIS transistor MP2 of a second conductivity type formed on the first active region 21a; and including a source/drain region formed of a Si mixed crystal layer buried in a recess; a second MIS transistor MN2 of a first conductivity type formed on the second active region 21b; and an isolation MIS transistor DP2 of the second conductivity type formed on the first active region 21a. The source/drain region of the first MIS transistor is not in contact with the isolation region 2 located at an end of the first active region 21a in a gate length direction.