Method of manufacturing a semiconductor device

A semiconductor device having a first MISFET comprising:

• a first well of a first conduction type formed in a semiconductor substrate;
• a gate insulating film of the first MISFET formed over the semiconductor substrate;
• a gate electrode of the first MISFET formed over the gate insulating film;
• first semiconductor regions of a second conduction type opposite to the first conduction type formed in the first well and serving as part of source and drain regions of the first MISFET;
• second semiconductor regions of the second conduction type formed in the first well, having a lower impurity concentration than that of the first semiconductor regions and serving as part of source and drain regions of the first MISFET;
• and
• an insulating film formed in the first well and embedded into a trench formed in the semiconductor substrate;
• wherein the second semiconductor regions surround the first semiconductor regions and the insulating film,
• wherein, in a gate length direction of the first MISFET, the insulating film is arranged between the first semiconductor regions and a channel region under the gate insulating film,
• wherein, in the gate length direction, ends of the gate electrode are formed over the insulating film,
• wherein third semiconductor regions of the first conduction type are formed at ends of the channel region in a gate width direction of said MISFET, and the third semiconductor regions are away from the source and drain regions of the first MISFET, and
• wherein an impurity concentration of the third semiconductor regions is higher than that of the first well.