Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising:

• forming a release layer including a first polycrystalline semiconductor layer, a second polycrystalline semiconductor layer, and a third polycrystalline semiconductor layer, the first polycrystalline semiconductor layer disposed on a first substrate, the second polycrystalline semiconductor layer disposed between the first substrate and the first polycrystalline semiconductor layer, the second polycrystalline semiconductor layer having a p-type impurity concentration lower than that of the first polycrystalline semiconductor layer, the third polycrystalline semiconductor layer disposed on the first polycrystalline semiconductor layer, the third polycrystalline semiconductor layer having a p-type impurity concentration lower than that of the first polycrystalline semiconductor layer;
• forming a first porous layer, a second porous layer, and a third porous layer by subjecting the first polycrystalline semiconductor layer, the second polycrystalline semiconductor layer, and the third polycrystalline semiconductor layer to anodic chemical conversion, respectively;
• forming a first device layer on the third porous layer;
• and
• bonding together the first device layer and a second device layer disposed on a second substrate.