Semiconductor device and preparation method thereof

The invention provides a semiconductor device and a preparation method thereof, and relates to the technical field of semiconductors, and the method comprises the steps: removing a conductive channel on a drift layer to form a passive structure; forming a first source metal and a first drain metal on the drift layer of the passive structure, wherein the first gate metal is located between the first source metal and the first drain metal; forming a second passivation layer on the first gate metal; and forming a source field plate on a second passivation layer. A first open-circuit test structure is highly similar to an actual device structure, and the difference is that a conductive channel is removed through a microelectronic or semiconductor preparation process, so that the first open-circuit test structure forms a passive test structure without a grid control function, and therefore, when an existing open-circuit de-embedding structure is matched, Cpg and Cpd, including Cpg1, Cpg2, Cpg3, Cpd1 and Cpd2, can