Insulated gate type semiconductor device and method for fabricating the same

A semiconductor device including a transistor, comprising:

• a semiconductor substrate of a first conductivity type;
• a first trench formed in the semiconductor substrate;
• a first impurity region of a second conductive type opposite 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 conductivity 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 conductivity 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 the second impurity region;
• and
• a second conductive film formed in the second trench, wherein the second conductive film is electrically connected with the first, second, and third impurity regions inside of the second trench,
• wherein the third impurity region is separated from the second impurity region.