FIG. 4 illustrates a partial cross-sectional view of another embodiment of a trench-based semiconductor device 400. The embodiment shown in FIG. 4 is similar to the embodiments shown in FIGS. 1 and 3. Different, however, the diffusion barrier structure 132 is omitted from the bottom of the contact trench 124 and therefore does not limit the vertical out-diffusion of the source/body contact doping. According to this embodiment, dopant out-diffusion from the highly doped body contact region 128 is vertically directed deeper into the drift zone/Si substrate 122/104. The diffusion barrier structure 132 may be omitted from the bottom of the contact trench 132 by epitaxially growing the alternating layers of Si 134 and oxygen-doped Si 136 only on the sidewall and not the bottom of the contact trench 124. For example, a dielectric spacer (not shown) may be formed at the bottom of the contact trench 124 to prevent epitaxial growth of the diffusion barrier structure 132 at the trench bottom.

FIGS. 5A through 5D illustrate respective cross-sectional views of another embodiment of omitting the diffusion barrier structure 132 from at least part of the bottom of the contact trench 124.