A solid-state image sensor includes: a trench isolation region; a photodiode region for converting incident light to signal charges and accumulating the signal charges therein; a floating diffusion region for accumulating the signal charges of the photodiode region; a gate electrode formed over the element formation region located between the photodiode region and the floating diffusion region, and formed so that both ends of the gate electrode respectively overlap a part of the photodiode region and a part of the floating diffusion region; and an inactive layer formed in a region located in a bottom portion and sidewall portions of the trench isolation region. An impurity concentration in a region located under the gate electrode in the inactive layer is lower than that in a region other than the region located under the gate electrode in the inactive layer.