A field effect transistor and a method for forming the field effect transistor are made up of a source region which is formed on the substrate, a drain region which is formed on the substrate, a stepped portion which is formed in the substrate between the source region and the drain region, a gate insulating film which is formed on the stepped portion of the substrate, and a gate electrode which is formed on the gate insulating film, wherein, a thickness of the gate insulating film near the drain region, which is less than that of the gate insulating film on a channel region defined in the substrate between the source region and the drain region. Accordingly, the field effect transistor and a method for forming the field effect transistor can prevent degradation of transistor characteristics because of a hot carrier effect.