Patent ID: 8771528

Claim:
A through-hole forming method comprising steps of: forming a first impurity region in a semiconductor substrate; forming a second impurity region in the semiconductor substrate, the second impurity region being formed around a region where a through-hole is to be formed; forming a first layer on a first surface of the semiconductor substrate; forming a mask layer on a second surface of the semiconductor substrate opposite to the first surface, the mask layer having an opening at a position corresponding to the through-hole to be formed; and etching the semiconductor substrate until at least the first layer is exposed via the opening, thereby forming the through-hole, wherein an impurity concentration of the first impurity region is higher than the semiconductor substrate, wherein an impurity concentration of the second impurity region is higher than the impurity concentration of the first impurity region, wherein the first and the second impurity regions are formed such that at least a part of the first impurity region and at least a part of the second impurity region are adjacent to each other in a depth direction of the semiconductor substrate, wherein the step of forming the first impurity region includes at least a first doping of impurities into a region having a first thickness; and wherein the step of forming the second impurity region includes at least a second doping, which is performed separately from the first doping, of impurities into a region having a second thickness smaller than the first thickness.