Method for manufacturing semiconductor device

1. A method for manufacturing a semiconductor device, the method comprising:

forming a front surface structure of a semiconductor element on a front surface side of a semiconductor substrate;

forming crystal defects in the semiconductor substrate by implanting charged particles into the semiconductor substrate;

subjecting the semiconductor substrate to a heat treatment after having formed the crystal defects;

attaching a supporting plate on the front surface side of the semiconductor substrate after the heat treatment;

thinning the semiconductor substrate by grinding a back surface side of the semiconductor substrate to which the supporting plate has been attached;

forming a back surface electrode on a back surface of the thinned semiconductor substrate; and

removing the supporting plate from the front surface side of the semiconductor substrate after forming the back surface structure.

2. The method as in claim 1 , wherein

the forming of the crystal defects comprises:

implanting the charged particles so that a first peak of crystal defect density is formed at a first depth from the front surface side of the semiconductor substrate; and

implanting the charged particles so that a second peak of the crystal defect density is formed at a second depth from the front surface side of the semiconductor substrate, wherein the second depth is shallower than the first depth,

the thinning of the semiconductor substrate comprises removing a part of the semiconductor substrate including a first depth region by grinding.

3. The method as in claim 1 , wherein the charged particles include at least one of helium ions, protons, and deuterons.