The invention provides a method for manufacturing a
transistor. The method comprises the steps of providing a substrate, wherein a false gate structure is formed on the substrate, the false gate structure comprises a
gate dielectric layer, a protective layer located on the
gate dielectric layer, an
oxide layer located on the protective layer and a false gate located on the
oxide layer, the
gate dielectric layer is made of
oxygen containing materials, and
oxygen diffuses to the upper surface of the protective layer, so that an oxidation layer is formed; forming the source
electrode and the drain
electrode of the
transistor after the false gate structure is formed; forming an interlayer
dielectric layer on the substrate after the source
electrode and the drain electrode are formed, wherein the upper surface of the false gate structure is exposed through the interlayer
dielectric layer; eliminating the false gate, wherein a false gate trench is formed in the interlayer
dielectric layer; eliminating the
oxide layer and the oxidation layer after the false gate trench is formed; forming a gate electrode in the false gate trench after the oxide layer and the oxidation layer are eliminated. By the adoption of the method for manufacturing the
transistor, the transistor can obtain an even
threshold voltage, and therefore the performance of the transistor is improved.