A semiconductor device has a gate electrode formed on a P type semiconductor substrate via gate oxide films. A first low concentration (LN type) drain region is made adjacent to one end of the gate electrode. A second low concentration (SLN type) drain region is formed in the first tow concentration drain region so that the second low concentration drain region is very close to the outer boundary of the second low concentration drain region and has at least a higher impurity concentration than the first low concentration drain region. A high concentration (N+ type) source region is formed adjacent to the other end of said gate electrode, and a high concentration (N+ type) drain region is formed in the second low concentration drain region having the designated space from one end of the gate electrode.