Semiconductor device including through-silicon via and method of forming the same

A semiconductor device comprising:

• a substrate comprising a first surface and a second surface opposing the first surface;
• a via insulating layer extending through the substrate, the via insulating layer having a width relatively increasing as the via insulating layer extends toward the first surface and having a width relatively decreasing as the via insulating layer extends toward the second surface;
• a through-silicon via extending through the via insulating layer, the through-silicon via having a width relatively decreasing as the through-silicon via extends toward the first surface and having a width relatively increasing as the through-silicon via extends toward the second surface;
• a blocking layer on the first surface;
• a first insulating layer on the blocking layer;
• and
• a contact plug contacting the through-silicon via and extending through the first insulating layer and the blocking layer.