A semiconductor device contains a first transistor including a single trench which is formed on a substrate between a source region and a drain region and a gate electrode which is formed in the single trench, a second transistor including at least two trenches which are formed on the substrate between a source region and a drain region and a gate electrode which is formed in the at least two trenches, and also contains a device isolation insulating which isolates the region in which the transistor is formed. The first transistor has first distance between the single trench and the device isolation insulating film and the second transistor has second distance between the adjoining trenches, such the first distance is less than the second distance in a gate width direction.