FIELD EFFECT TRANSISTOR

PURPOSE: To allow the channel width to be expanded by forming a contact region and source region on the front face formed up to the top ends of protrusions in a channel forming region and forming a gate oxide film on the surface of the channel forming region between the source region and extended drain region. CONSTITUTION: On the front face within an expanded drain region 41 are formed protrusions 44a directed to a drain region 43 with their top ends apart at specified distance from the drain region 43. On the extensions of the protrusions 44a a semiconductor substrate 41 and electrolytic relaxation layer 46 are formed. On the front face within a channel forming region 44 a source region 45 is formed up to near the top ends of the protrusions 44a and apart at specified distance from the outer end of this region 44. On the front face within this region 44 a contact region 47 is formed. A gate oxide film 48 is formed on the surface of the region 42 between the source region 45 and expanded drain region 42. This allows the channel width to be made wide.