A method of fabricating semiconductor devices includes forming a plurality of first and second semiconductor nanosheets in p-type and n-type device regions, respectively. An n-type work function layer is deposited to surround each of the first and second semiconductor nanosheets. A passivation layer is deposited on the n-type work function layer to surround each of the first and second semiconductor nanosheets. A patterned mask is formed on the passivation layer in the n-type device region, and the n-type work function layer and the passivation layer in the p-type device region are removed in an etching process using the patterned mask as an etching mask. Then, the patterned mask is removed, and a p-type work function layer is deposited to surround the first semiconductor nanosheets and to cover the passivation layer.