Solid state image device having a pair of overflow drains extends along the electron transfer direction at a boundary between channel region and channel stop isolation regions of the multiplication register
In a solid state imaging device with an electron multiplying function, in a section normal to an electron transfer direction of a multiplication register EM, an insulating layer 2 is thicker at both side portions than in a central region. A pair of overflow drains 1 N is formed at a boundary between a central region and both side portions of an N-type semiconductor region 1 C. Each overflow drain 1 N extends along the electron transfer direction of the multiplication register EM. Overflow gate electrodes G extend from the thin portion to the thick portion of the insulating layer 2 . The overflow gate electrodes G are disposed between both ends of each transfer electrode 8 in a longitudinal direction and the insulating layer 2 , and they also function as shield electrodes for each electrode 8 ( 8 A and 8 B).
1. A solid state imaging device with an electron multiplying function comprising:
an imaging region;
a horizontal shift register that transfers electrons from the imaging region; and
a multiplication register that multiplies the electrons from the horizontal shift register, wherein
the multiplication register includes
a semiconductor region,
an insulating layer formed on the semiconductor region,
a plurality of transfer electrodes formed adjacent to each other on the insulating layer; and
DC electrodes that are arranged between the transfer electrodes and to which a direct-current electric potential is applied, wherein
in a section normal to an electron transfer direction of the multiplication register, the insulating layer is thicker at both side portions than in a central region, and a pair of overflow drains is formed at a boundary between the central region and both the side portions of the semiconductor region, and
each of the overflow drains extends along the electron transfer direction of the multiplication register.
2. The solid state imaging device with the electron multiplying function according to claim 1 , wherein
the transfer electrodes positioned at a next stage of the DC electrodes are taken as multiplication electrodes, the solid state imaging device with the electron multiplying function further includes overflow gate electrodes insulated from the multiplication electrodes and the overflow drains and disposed between the multiplication electrodes and the overflow drains.
3. The solid state imaging device with the electron multiplying function according to claim 1 , further comprising
potential barrier regions disposed between the overflow drains and the semiconductor regions and that obstruct an influx of the electrons from the semiconductor regions to the overflow drains.
4. The solid state imaging device with the electron multiplying function according to claim 3 , wherein
the semiconductor region is comprised of an N-type semiconductor,
the potential barrier regions are comprised of an N-type semiconductor having an impurity concentration lower than the semiconductor region, and
the overflow drains are comprised of an N-type semiconductor having an impurity concentration higher than the semiconductor region.