Patent ID: 7612408
Filing Date: 2009-11-03
Classification: H01L

Abstract:
1. A trench transistor device having an upper semiconductor region and a lower semiconductor region, comprising: a substrate layer provided in the lower semiconductor region; at least a first and a second gate trench, each extending in a vertical direction through the upper semiconductor region and the lower semiconductor region toward but not into the substrate layer, and having a length defined in a first lateral direction and a thickness defined in a second lateral direction of the semiconductor regions, the first lateral direction crossing the second lateral direction; a gate electrode projecting in the vertical direction into the gate trench, insulated via an outer gate oxide, the gate electrode having a gate step beginning at a transition from the upper semiconductor region to the lower semiconductor region defining a field plate in the upper semiconductor region where the gate oxide in the second lateral direction is thinner than in the lower semiconductor region; and a dense trench mesa region formed in the upper semiconductor region in parallel with and between the first and second gate trenches, said dense trench mesa region having a length extending in the first lateral direction and a width in the second lateral direction between the first and second gate trenches which is less than 2.5 times a maximum thickness of the gate oxide in the gate trenches, said dense trench mesa region comprising the following semiconductor regions: a source electrode, a body region extending below the source electrode, and a body contact region extending above the body region but not to a depth of the gate step; a body reinforcement positioned below the body region only at the location of the body contact region and extending in vertical direction through a portion of the upper region to a depth below the gate step but not extending to the substrate layer; and said source electrode and said body contact region being alternately provided at the top most section of the mesa region in the first lateral direction and widths of said source electrode, said body region, said body contact region and said body reinforcement defined in the second lateral direction being equal to the width of the mesa region.