A solid-state image sensor is provided. The sensor includes a first transistor including a first diffusion region, a second transistor including a second diffusion region and an insulation film arranged over these transistors. The insulation film includes a first and a second film. A first portion of the first diffusion region covered with the insulation film includes a second portion covered with only the second film. A third portion of the second diffusion region covered with the insulation film includes a fourth portion covered with the first and second film. A stress in the fourth portion is larger than the second portion. A proportion of an area of the first portion except the second portion to an area of the first portion is lower than a proportion of an area of the fourth portion to an area of the third portion.