The invention discloses a
semiconductor structure and a formation method thereof. The method comprises the steps of providing a substrate, a fin portion and channel laminations located on the fin portion, wherein each channel lamination comprises sacrificial
layers and channel
layers, if the number of the channel laminations is two, the sacrificial layer close to the top of the channel laminationis a first sacrificial layer, the remaining sacrificial layer is a second sacrificial layer, and if the number of the channel laminations is greater than or equal to three, at least one sacrificial layer close to the top of the channel lamination is a first sacrificial layer, and the remaining sacrificial
layers are second sacrificial layers; forming a pseudo gate structure;
etching the channel lamination layers on two sides of the pseudo gate structure to form grooves;
etching part of the first sacrificial layer exposed out of the groove to form a first trench; forming a first
barrier layer in the first trench;
etching part of the second sacrificial layer exposed out of the groove to form a second trench, wherein the depth of the second trench is greater than that of the first trench; forming a second
barrier layer in the second trench; forming a source-drain
doping layer in the groove; and forming a
metal gate structure at the positions of the pseudo gate structure, the remaining first sacrificial layer and the remaining second sacrificial layer. The forming quality of the
metal gate structure is improved according to the invention.