Semiconductor substrate, semiconductor device, and manufacturing methods thereof

A method of manufacturing a semiconductor substrate, the method comprising:

• forming a first semiconductor layer on a substrate;
• forming a metallic material layer on a first portion of the first semiconductor layer;
• forming a second semiconductor layer on the first semiconductor layer and the metallic material layer;
• and
• forming a cavity in a portion of the first semiconductor layer directly under the metallic material layer along a line perpendicular to the plane of the substrate,
• wherein:
• the second semiconductor layer directly contacts a second portion of the first semiconductor layer;
• the metallic material layer comprises titanium or chromium;
• and
• the semiconductor substrate is formed by separating the substrate from the first semiconductor layer and the second semiconductor layer using the cavity formed in the first semiconductor layer.