Semiconductor device and method of fabricating the same

A semiconductor integrated circuit comprising:

• an HVMISFET (high withstand voltage MOSFET) having:
• a source region and a drain region of a second conductivity type formed apart from each other on a surface of a semiconductor region of a first conductivity type,
• a channel-forming region which is the surface of the semiconductor region between the source region and the drain region,
• a gate formed on the channel-forming region via a gate insulating film,
• the drain region being constituted of a low concentration drain region and a high-concentration drain region in contact with each other,
• the low-concentration drain region being disposed between the channel-forming region and the high concentration drain region,
• a field insulating film with a thickness at least one order of ten greater than that of the gate insulating film and located directly above the low-concentration drain region;
• and
• a region diffused with elemental boron formed on the surface of the low concentration drain region and located directly between the field insulating film and the low concentration drain region;
• and
• an LVMISFET (low withstand voltage MOSFET) of the same conductivity type farmed on the same semiconductor region and having the same threshold voltage and gate insulating film as the HVMISFET.