A semiconductor structure includes a dielectric layer located on a substrate, wherein the dielectric layer includes nitrogen atoms, and the concentration of the nitrogen atoms in the dielectric layer is lower than 5% at a location wherein the distance between this location in the dielectric layer to the substrate is less than 20% of the thickness of the dielectric layer. Moreover, the present invention provides a semiconductor process including the following steps: a dielectric layer is formed on a substrate. Two annealing processes are performed in-situly on the dielectric layer, wherein the two annealing processes have different imported gases and different annealing temperatures.