Semiconductor substrate formed by epitaxially filling a trench in a semiconductor substrate with a semiconductor material after smoothing the surface and rounding the corners

A semiconductor substrate comprising:

• a trench formed in a semiconductor substrate, wherein the trench is open at an upper surface of the semiconductor substrate, wherein the depth of the trench is between 10 μm and 50 μm, and wherein a radius of curvature at a corner defined by a side face and a bottom face of the trench is 1.0 μm or more, and the maximum roughness height of an inner face of the trench is 3 nm or less due to a thermal treatment in a hydrogen atmosphere;
• and
• a single crystal semiconductor layer filling the trench, wherein the single crystal semiconductor layer is formed by filling the trench with an epitaxial film after a heat treatment is applied to the trench in a non-oxidizing or non-nitriding atmosphere under a low pressure, wherein the semiconductor substrate is a silicon substrate having a (110) face orientation, and wherein a side surface of the trench has a (111) face orientation, and a bottom surface of the trench has a (110) face orientation.