一种制造半导体设备的方法包含：形成鳍片结构，其中包含锗的多个第一半导体层与多个第二半导体层交替地层叠于该鳍片结构的底部上；增加第一半导体层中的锗浓度；于鳍片结构上形成牺牲闸极结构；于鳍片结构的源极/汲极区上形成源极/汲极磊晶层；移除牺牲闸极结构；移除于信道区中的第二半导体层，从而释放锗浓度增加的第一半导体层；以及在第一半导体层周围形成闸极结构，其中锗浓度增加。

In a method of manufacturing a semiconductor device, a fin structure, in which first semiconductor layers containing Ge and second semiconductor layers are alternately stacked, is formed over a bottom fin structure. A Ge concentration in the first semiconductor layers is increased. A sacrificial gate structure is formed over the fin structure. A source/drain epitaxial layer is formed over a source/drain region of the fin structure. The sacrificial gate structure is removed. The second semiconductor layers in a channel region are removed, thereby releasing the first semiconductor layers in which the Ge concentration is increased. A gate structure is formed around the first semiconductor layers in which the Ge concentration is increased.