| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a flat substrate for a semiconductor element with less defects by simple processes. SOLUTION: An AlN buffer layer 12 is formed with the film thickness of about 20 nm at a temperature 500 deg.C on an SiC substrate 11, the temperature is turned to 1050 deg.C, and a GaN layer 13 is grown for about 3μm. Then, an SiO2 film 14 is formed and the pattern of lines and spaces is formed with the interval of about 24μm so as to leave the SiO2 film 14 of the width of 16μm. The GaN layer 13 is removed for the depth of about 2μm by dry etching and trapezoidal groove stripes are formed. The GaN layer 16 is selectively grown for about 6μm. At the time, since horizontal direction growth is fast, the surface of a groove upper part is finally flattened. At the time, the area 16a of a low defect density is formed on a groove upper surface other than the intermediate part of the widthwise direction of the groove. The SiO2 film 17 is formed, resist 18 is applied and then the resist 18 and the SiO2 film 17 other than the area separated for about 2μm from an end on one side of the area 16a of the low defect density of the groove part are removed. The GaN layer 16 to the upper surface of the SiC substrate 11 or a part of the substrate is removed. The GaN layer 19 is selectively grown for about 10μm.
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