| CPC H10D 30/015 (2025.01) [H01L 21/3081 (2013.01); H10D 30/4755 (2025.01); H10D 62/824 (2025.01); H10D 62/8503 (2025.01)] | 9 Claims |

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1. A method for fabricating a high electron mobility transistor (HEMT), comprising:
forming a buffer layer on a substrate;
forming a first barrier layer on the buffer layer;
forming a second barrier layer on the first barrier layer;
forming a first hard mask on the second barrier layer;
forming a second hard mask on the first hard mask, wherein the first hard mask and the second hard mask comprise different materials;
patterning the second hard mask, the first hard mask, the second barrier layer, the first barrier layer, and the buffer layer;
forming a third hard mask on a top surface and sidewalls of the patterned second hard mask;
removing the patterned first hard mask and the patterned second barrier layer to form a recess;
forming a p-type semiconductor layer in the recess; and
forming a source electrode and a drain electrode adjacent to two sides of the p-type semiconductor layer.
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