A semiconductor device includes a device isolation insulating film which is buried in a semiconductor substrate, a gate insulation film which is provided on the semiconductor substrate, a gate electrode which is provided on the gate insulation film, a source region and a drain region which are provided in the semiconductor substrate and spaced apart from each other in a manner to sandwich the gate electrode, both end portions of each of the source region and the drain region being offset from the device isolation insulating film in a channel width direction by a predetermined distance, and first and second gate electrode extension portions which are provided in a manner to cover both end portions of each of the source region and the drain region in a channel length direction.