Solid state imaging device having impurity concentration on light receiving surface being greater or equal to that on opposing surface
A solid-state imaging device includes: a first photodiode made up of a first first-electroconductive-type semiconductor region formed on a first principal face side of a semiconductor substrate, and a first second-electroconductive-type semiconductor region formed within the semiconductor substrate adjacent to the first first-electroconductive-type semiconductor region; a second photodiode made up of a second first-electroconductive-type semiconductor region formed on a second principal face side of the semiconductor substrate, and a second second-electroconductive-type semiconductor region formed within the semiconductor substrate adjacent to the second first-electroconductive-type semiconductor region; and a gate electrode formed on the first principal face side of the semiconductor substrate; with impurity concentration of a connection face between the second first-electroconductive-type semiconductor region and the second second-electroconductive-type semiconductor region being equal to or greater than impurity concentration of a connection face of an opposite layer of the second first-electroconductive-type semiconductor region of the second second-electroconductive-type semiconductor region.
1. A solid-state imaging device comprising:
a first photodiode including:
a first first-electroconductive-type semiconductor region on a first principal face side of a semiconductor substrate,
a first second-electroconductive-type semiconductor region within said semiconductor substrate adjacent to said first first-electroconductive-type semiconductor region, and
a second second-electroconductive-type semiconductor region within said semiconductor substrate and adjacent to said first second-electroconductive-type semiconductor region;
a second photodiode including:
a second first-electroconductive-type semiconductor region on a second principal face side of said semiconductor substrate,
a third second-electroconductive-type semiconductor region within said semiconductor substrate between said first first-electroconductive-type semiconductor region and said second first-electroconductive-type semiconductor region, wherein the third second-electroconductive-type semiconductor region is adjacent to said second first-electroconductive-type semiconductor region, and
a fourth second-electroconductive-type semiconductor region within said semiconductor substrate and adjacent to said third second-electroconductive-type semiconductor region and said second second-electroconductive-type semiconductor region, wherein said second second-electroconductive-type semiconductor region of said first photodiode and said fourth second-electroconductive-type semiconductor region of said second photodiode are connected at a center of the semiconductor substrate; and
a gate electrode on the first principal face side of said semiconductor substrate,
wherein an impurity concentration of the third second-electroconductive-type semiconductor region at a connection face between said second first-electroconductive-type semiconductor region and said third second-electroconductive-type semiconductor region is equal to or greater than an impurity concentration of the fourth second-electroconductive-type semiconductor region at a connection face between said second second-electroconductive-type semiconductor region and said fourth second-electroconductive-type semiconductor region, and
wherein a potential at the connection face between said second second-electroconductive-type semiconductor region and said fourth second-electroconductive-type semiconductor region is lower than a potential at a connection face between said third second-electroconductive-type semiconductor region and said fourth second-electroconductive-type semiconductor region.
2. The solid-state imaging device according to claim 1 , further comprising a first pixel separation portion and a second pixel separation portion of a first-electroconductive-type semiconductor region, wherein the first pixel separation portion and the second pixel separation portion are between adjacent pixels.
3. The solid-state imaging device according to claim 2 , wherein the first principal face side of the semiconductor substrate comprises the first pixel separation portion and the second principal face side of the semiconductor substrate comprises the second pixel separation portion.
4. The solid-state imaging device according to claim 2 , further comprising a floating diffusion region in at least one of the first and second pixel separation portions.
5. The solid-state imaging device according to claim 4 , wherein the floating diffusion region of a second-electroconductive-type semiconductor region is on at least one of the first principal face side of the semiconductor substrate and the second principal face side of the semiconductor substrate.
6. The solid-state imaging device according to claim 2 , wherein the first pixel separation region and the second pixel separation region are connected at the center of the semiconductor substrate.
7. An electronic device comprising:
a solid-state imaging device having:
a first photodiode including:
a first first-electroconductive-type semiconductor region on a first principal face side of a semiconductor substrate,
a first second-electroconductive-type semiconductor region within said semiconductor substrate adjacent to said first first-electroconductive-type semiconductor region, and
a second second-electroconductive-type semiconductor region within said semiconductor substrate and adjacent to said first second-electroconductive-type semiconductor region;
a second photodiode including:
a second first-electroconductive-type semiconductor region on a second principal face side of said semiconductor substrate, and
a third second-electroconductive-type semiconductor region within said semiconductor substrate between said first first-electroconductive-type semiconductor region and said second first-electroconductive-type semiconductor region, wherein the third second-electroconductive-type semiconductor region is adjacent to said second first-electroconductive-type semiconductor region, and
a fourth second-electroconductive-type semiconductor region within said semiconductor substrate and adjacent to said third second-electroconductive-type semiconductor region and said second second-electroconductive-type semiconductor region, wherein said second second-electroconductive-type semiconductor region of said first photodiode and said fourth second-electroconductive-type semiconductor region of said second photodiode are connected at a center of the semiconductor substrate; and
a gate electrode on the first principal face side of said semiconductor substrate,
wherein an impurity concentration of the third second-electroconductive-type semiconductor region at a connection face between said second first-electroconductive-type semiconductor region and said third second-electroconductive-type semiconductor region is equal to or greater than an impurity concentration of the fourth second-electroconductive-type semiconductor region at a connection face between said second second-electroconductive-type semiconductor region and said fourth second-electroconductive-type semiconductor region, and
wherein a potential at the connection face between said second second-electroconductive-type semiconductor region and said fourth second-electroconductive-type semiconductor region is lower than a potential at a connection face between said third second-electroconductive-type semiconductor region and said fourth second-electroconductive-type semiconductor region;
an optical system configured to guide incident light into an imaging unit of said solid-state imaging device; and
a signal processing circuit configured to process an output signal of said solid-state imaging device.
8. The electronic device according to claim 7 , further comprising:
a planar-type transfer transistor configured to read out charges of said first photodiode on a first principal face of said semiconductor substrate; and
a vertical-type transfer transistor configured to read out charges of said second photodiode on the first principal face of said semiconductor substrate.
9. The electronic device according to claim 7 , further comprising, a first pixel separation portion and a second pixel separation portion of a first-electroconductive-type semiconductor region, wherein the first pixel separation portion and second pixel separation portion are between adjacent pixels.
10. The electronic device according to claim 9 , wherein the first principal face side of the semiconductor substrate comprises the first pixel separation portion and the second principal face side of the semiconductor substrate comprises the second pixel separation portion.
11. The electronic device according to claim 9 , further comprising a floating diffusion region in at least one of the first and second pixel separation portions.
12. The electronic device according to claim 11 , wherein the floating diffusion region of a second-electroconductive-type semiconductor region is on at least one of the first principal face side of the semiconductor substrate and the second principal face side of the semiconductor substrate.