Patent ID: 7667265

Claim:
A field effect transistor comprising: a first plurality of cells having a first cell pitch, the first plurality of cells having gates with first mesa regions extending between the gates, wherein a heavy body contact opening extends into each first mesa region, and a heavy body region extends in each first mesa regions along a bottom of corresponding heavy body contact opening; and a second plurality of cells having a second cell pitch, the second cell pitch being narrower than the first cell pitch, the second plurality of cells having gates with second mesa regions extending between the gates, wherein no heavy body contact opening is formed in the second mesa regions, and a heavy body region extends in each second mesa region to a shallower depth than a depth to which the heavy body regions in the first mesa regions extend; wherein each of the gates in the first and second plurality of cells is housed in a trench, each mesa region in the first and second plurality of cells including a well region, the well regions in at least the second plurality of cells including source regions having a conductivity type opposite that of the well regions; wherein each of the heavy body regions in the first and the second mesa regions is located in a corresponding well region, the heavy body regions being of the same conductivity type as but having a higher doping concentration than the well regions.