Insulated gate type semiconductor device and method for fabricating the same

A semiconductor device including a MISFET, comprising:

• a semiconductor substrate of a first conductive type;
• a first trench formed in the semiconductor substrate;
• a first conductive film embedded in the first trench and protruding from a top surface of the semiconductor substrate;
• a cap insulating film formed over the first conductive film;
• a first impurity region of a second conductive type opposite to the first conductive type formed in the semiconductor substrate, wherein a depth of the first impurity region is shallower than a depth of the first trench;
• a second impurity region of the first conductive type formed in the semiconductor substrate, wherein a depth of the second impurity region is shallower than the depth of the first impurity region;
• a second trench formed in the semiconductor substrate, wherein the second trench penetrates the second impurity region and reaches the first semiconductor impurity region, and wherein a depth of the second trench is shallower than a depth of the first trench;
• a third impurity region of the second conductive type formed in the first impurity region located at a bottom of the second trench, wherein an impurity concentration of the third impurity region is higher than an impurity concentration of the first impurity region;
• a first insulating film formed over a side surface of the cap insulating film, over a side surface of the first conductive film and over the second impurity region, wherein a part of a top surface of the second impurity region is exposed from the first insulating film;
• and
• a second conductive film formed in the second trench, wherein the second conductive film is electrically connected with the top surface of the second impurity region outside of the second trench and is electrically connected with the first, second and third impurity regions inside of the second trench.