Method of forming a nitride-based semiconductor
A nitride-based semiconductor element having excellent element characteristics is obtained by forming a nitride-based semiconductor layer having excellent crystallinity without performing a long etching process. This nitride-based semiconductor element and the method thereof includes forming a mask layer having a recess portion on a substantially flat upper surface of an underlayer to partially expose the upper surface of the underlayer. A nitride-based semiconductor layer is laterally grown on the exposed part of the underlayer and the mask layer while forming a void on the recess portion of the mask layer. Thus, the strain of the laterally grown nitride-based semiconductor layer is so relaxed that the crystallinity of the nitride-based semiconductor layer is improved.
1. A method of forming a nitride-based semiconductor comprising steps of:
forming a mask layer having an overhanging shape on a substantially flat upper surface of an underlayer to expose part of said flat upper surface of said underlayer; and
growing a nitride-based semiconductor layer on said exposed part of said underlayer and said mask layer.
2. The method of forming a nitride-based semiconductor according to claim 1 , wherein
said step of growing said nitride-based semiconductor layer includes a step of growing said nitride-based semiconductor layer from under said mask layer having an overhanging shape and applying force from under the overhang of said mask layer thereby curving the upper surface of said overhanging mask layer.
3. The method of forming a nitride-based semiconductor according to claim 1 , wherein
said step of forming said mask layer includes steps of:
forming a first mask material layer on said underlayer while forming a second mask material layer having a smaller etching rate than said first mask material layer on said first mask material layer, and
etching said first mask material layer and said second mask material layer thereby forming said overhanging mask layer having said first mask material layer and said second mask material layer.
4. The method of forming a nitride-based semiconductor according to claim 1 , wherein
said underlayer includes a substrate, and
said step of forming said mask layer includes a step of forming said mask layer to be in contact with the upper surface of said substrate.
5. The method of forming a nitride-based semiconductor according to claim 1 , further comprising a step of growing a nitride-based semiconductor element layer having an element region on said nitride-based semiconductor layer.