Patent ID: 7696571
Filing Date: 2010-04-13
Classification: H01L

Abstract:
1. A field effect transistor comprising: a semiconductor substrate having dopants of a first conductivity type; a trench extending a predetermined depth into the semiconductor substrate, wherein a gate structure is formed inside the trench; a doped well having dopants of a second conductivity type opposite to the first conductivity type and extending into the semiconductor substrate to form a well junction at a first depth; a doped source region having dopants of the first conductivity type and extending into the semiconductor substrate to form a source junction at a second depth; and a doped heavy body region having dopants of the second conductivity type and extending into the doped well to form a heavy body junction at a depth that is deeper than the source junction and shallower than the well junction, the doped heavy body region having a region of high dopant concentration near the junction with the doped well and a region of relatively low dopant concentration near the surface of the substrate, the depth of the doped heavy body region relative to the depth of the doped well is selected so that a peak electric field, when voltage is applied to the transistor, is spaced away from the trench.