Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising:

• preparing a substrate unit comprising a base substrate, an intermediate crystal layer provided on the base substrate, and a first mask layer, the base substrate having a first coefficient of thermal expansion, the intermediate crystal layer having a first lattice constant, the intermediate crystal layer having a major surface having a first region, a second region, and a first intermediate region provided between the first region and the second region, the second region being separated from the first region in a first direction perpendicular to a stacking direction from the base substrate toward the intermediate crystal layer, the first mask layer being provided on the first intermediate region, and wherein the first mask layer is not provided on the first region and is not provided on the second region;
• implementing a first growth to grow a first lower layer on the first region at a 1st temperature and grow a second lower layer on the second region at the first temperature, the first lower layer comprising a semiconductor crystal having a second coefficient of thermal expansion larger than the first coefficient of thermal expansion and a second lattice constant larger than the first lattice constant, the second lower layer comprising the semiconductor crystal;
• implementing, at a second temperature, a second growth to grow a second upper layer comprising the semiconductor crystal on the second lower layer to extend onto the first mask layer while growing a first upper layer comprising the semiconductor crystal on the first lower layer to extend onto the first mask layer to cover the first mask layer with the first upper layer and the second upper layer by causing the first upper layer and the second upper layer to contact each other on the first mask layer;
• and
• implementing cooling to separate the first upper layer and the second upper layer from each other at a first boundary where the first upper layer and the second upper layer contact each other on the first mask layer by reducing a temperature of the substrate unit, the first lower layer, the second lower layer, the first upper layer, and the second upper layer to a third temperature lower than the first temperature and the second temperature;
• wherein the major surface further comprises:
• a third region separated from the first region in a second direction non-parallel to the first direction;
• and
• a second intermediate region provided between the first region and the third region, the substrate unit further comprises a second mask layer provided on the second intermediate region, the implementing of the first growth comprises growing a third lower layer comprising the semiconductor crystal on the third region at the first temperature, the growing of the first upper layer comprises growing the first upper layer to further extend onto the second mask layer, the implementing of the second growth comprises:
• growing, at the second temperature, a third upper layer comprising the semiconductor crystal on the third lower layer to extend onto the second mask layer;
• and covering the second mask layer with the first upper layer and the third upper layer by causing the first upper layer and the third upper layer to contact each other on the second mask layer, and the implementing of the cooling further comprises separating the first upper layer and the third upper layer from each other at a second boundary where the first upper layer and the third upper layer contact each other on the second mask layer by reducing the temperature of the third lower layer and the third upper layer to the third temperature.