A solid-state image sensor comprises a semiconductor substrate of a first
conductivity type having a color pixel region and a black pixel region; a
first well of the first conductivity type formed in the color pixel
region; a second well of the first conductivity type formed in the black
pixel region; a third well of a second conductivity type formed,
surrounding the second well and isolating the second well from the rest
region of the semiconductor substrate; a color pixel formed in the first
well in the color pixel region and including a first photodiode and a
first read transistor for reading a signal generated by the first
photodiode; and a black pixel formed in the second well in the black
pixel region and including a second photodiode and a second read
transistor for reading a signal generated by the second photodiode. The
first well includes a first buried impurity doped layer of the first
conductivity type formed in a bottom thereof in a region where the first
read transistor is formed. The second well includes a second buried
impurity doped layer of the first conductivity type formed in a bottom
thereof in a region where the second photodiode is formed and a region
where the second read transistor is formed.