A fin field-effect transistor structure includes a substrate, a fin channel and a high-k metal gate. The high-k metal gate is formed on the substrate and the fin channel. A process of manufacturing the fin field-effect transistor structure includes the following steps. Firstly, a polysilicon pseudo gate structure is formed on the substrate and a surface of the fin channel. By using the polysilicon pseudo gate structure as a mask, a source/drain region is formed in the fin channel. After the polysilicon pseudo gate structure is removed, a high-k dielectric layer and a metal gate layer are successively formed. Afterwards, a planarization process is performed on the substrate having the metal gate layer until the first dielectric layer is exposed, so that a high-k metal gate is produced.