3d semiconductor structure and method of fabricating the same

A method of fabricating a 3D semiconductor structure, comprising:

• providing a substrate;
• sequentially forming a doped aluminum gallium nitride barrier layer, a doped gallium nitride channel layer, a buffer layer, an undoped gallium nitride channel layer and an undoped aluminum gallium nitride barrier layer on said substrate, wherein a two-dimensional electron gas (2DEG) is formed in said doped gallium nitride channel layer, and a two-dimensional hole gas (2DHG) is formed in said undoped gallium nitride channel layer;
• forming a first gate, a first source and a first drain on said undoped aluminum gallium nitride barrier layer, wherein said undoped gallium nitride channel layer, said undoped aluminum gallium nitride barrier layer, said first gate, said first source and said first drain form a n-type high electron mobility transistor;
• covering a first passivation layer on said undoped aluminum gallium nitride barrier layer, said first gate, said first source and said first drain;
• flipping said substrate and removing said substrate to expose said doped aluminum gallium nitride barrier layer;
• and
• forming a second gate, a second source and a second drain on said doped aluminum gallium nitride barrier layer, wherein said doped gallium nitride channel layer, said doped aluminum gallium nitride barrier layer, said second gate, said second source and said second drain form a p-type high hole mobility transistor.