A trench capacitor comprises a semiconductor substrate, a trench, formed in the
semiconductor substrate, having upper and lower portions, a first doped polysilicon
layer filled in the lower portion through a first dielectric film and doped with
a first impurity having a first conductivity type, at least a second doped polysilicon
layer filled in the upper portion through a second dielectric film and doped with
a second impurity different from the first impurity, the second impurity having
the first conductivity type, and a buried strap layer provided on the second doped
polysilicon layer and composed of the first doped polysilicon layer.
