Crystal growth method for nitride semiconductor and formation method for semiconductor device

A method of crystal growth for a nitride semiconductor, the method comprising the steps of:

• forming a plurality of island crystal regions on a base body of the nitride semiconductor using vapor-phase growth during a first crystal growth phase including a first crystal growth rate and a first crystal growth temperature wherein the island crystal regions each include a boundary region;
• continuing growth of the island crystal regions while bonding of the boundary regions during a second crystal growth phase including a second crystal growth phase rate and a second crystal growth temperature wherein at least one of the second crystal growth rate is greater than the first crystal growth rate and the second crystal growth temperature is lower than the first crystal growth temperature;
• and
• changing from the first crystal growth phase to the second crystal growth phase once a state of irregularities on a surface portion of the base body is observed.

A method of manufacturing a semiconductor device, the method comprising the steps of:

• forming a plurality of island crystal regions on a base body of a nitride semiconductor using vapor-phase growth at a first crystal growth rate wherein the island crystal regions each include a boundary region;
• continuing growth of the island crystal regions at a second crystal growth rate greater than the first crystal growth rate while bonding of the boundary regions occurs;
• and
• forming the semiconductor device on a layer of the nitride semiconductor formed by bonding the boundary regions of the island crystal regions.

A method of forming a semiconductor device, the method comprising the steps of:

• forming a plurality of island crystal regions on a base body of a nitride semiconductor using vapor-phase growth at a first crystal growth temperature wherein the island crystal regions each include a boundary region;
• continuing growth of the island crystal regions at a second crystal growth temperature lower than the first crystal growth temperature while bonding of the boundary regions of the island crystal regions occurs;
• and
• forming a semiconductor device on a layer of the nitride semiconductor formed by bonding the boundary regions of the island crystal regions.