Resistance ladder together with digital-analog converter and semiconductor using the same

A resistance ladder formed by connecting together a plurality of resistance groups, where each of said resistance groups has at least first to third resistors extending along a longitudinal axial direction, said resistance ladder comprising:

• a first insulation layer formed on top of each of said first to third resistors and having first contact holes at positions corresponding to end portion in said longitudinal axial direction of each of said first to third resistors;
• a first wiring layer formed on top of said first insulation layer, connecting together said first to third resistors via said contact holes;
• a dummy wiring layer formed as the same layer as said first wiring layer and corresponding to said first to third resistors;
• a second insulation layer formed on top of said first wiring layer and said dummy wiring layer and having second contact holes at positions corresponding to said first wiring layer;
• and
• a second wiring layer formed on top of said second insulation layer and connecting together adjacent resistance groups via second said contact holes.

A digital-to-analog converter for converting an n-bit digital signal into an analog signal, said digital-to-analog converter comprising:

• a resistance ladder formed by connecting together n resistance groups, where each of said resistance groups has at least first to third resistors extending along a longitudinal axial direction;
• and
• n driver circuits connected each to one of said resistance groups and also disposed in a line on the same side of said resistance groups;
• wherein said resistance ladder comprises:
• an insulation layer formed on top of each of said first to third resistors of each of said resistance groups and having contact holes at positions corresponding to end portions in said longitudinal axial direction of each of said first to third resistors;
• a first wiring layer formed on top of said insulation layer, connecting together said first and second resistors and said second and third resistors within each of said resistance groups via said contact holes;
• and
• a second wiring layer formed as the same layer as said first wiring layer and connecting together adjacent resistance groups;
• wherein said second and third resistors in each of said resistance groups are disposed parallel to said longitudinal axial direction and on either side of said first resistor;
• wherein said second wiring layer connects together one end in said longitudinal axial direction of said first resistor of one of said adjacent resistance groups to the other end in said longitudinal axial direction of said first resistor of another of said adjacent resistance groups, and is also formed to extend over other resistors positioned between said first resistors of said adjacent resistance groups;
• and
• wherein surface areas of said second wiring layer corresponding to each of said first to third resistors in each of said resistance groups are set to be substantially equal.

A digital-to-analog converter for converting an n-bit digital signal into an analog signal, said digital-to-analog converter comprising:

• a resistance ladder formed by connecting together n resistance groups, where each of said resistance groups has at least first to third resistors extending along a longitudinal axial direction;
• and
• n driver circuits connected each to one of said resistance groups;
• wherein said resistance ladder comprises:
• a first insulation layer formed on top of each of said first to third resistors and having first contact holes at positions corresponding to end portion in said longitudinal axial direction of each of said first to third resistors;
• a first wiring layer formed on top of said first insulation layer, connecting together said first to third resistors via said first contact holes;
• a dummy wiring layer formed as the same layer as said first wiring layer and corresponding to said first to third resistors;
• a second insulation layer formed on top of said dummy wiring layer and having second contact holes at positions corresponding to said first wiring layer;
• and
• a second wiring layer formed on top of said second insulation layer and connecting together adjacent resistance groups via said second contact holes.

A digital-to-analog converter for converting an n-bit digital signal into an analog signal, said digital-to-analog converter comprising:

• a resistance ladder formed by connecting together n resistance groups, where each of said resistance groups has at least first to third resistors extending along a longitudinal axial direction;
• and
• n driver circuits connected each to one of said resistance groups;
• wherein said resistance ladder comprises:
• a first insulation layer formed on top of each of said first to third resistors of each of said resistance groups and having contact holes corresponding to end portions in said longitudinal axial direction of each of said first to third resistors;
• a first wiring layer formed on top of said first insulation layer, connecting together said first and second resistors and said second and third resistors within each of said resistance groups via said contact holes;
• and
• a second wiring layer formed as the same layer as said first wiring layer and connecting together adjacent resistance groups;
• wherein said second and third resistors in each of said resistance groups are disposed parallel to said longitudinal axial direction and on either side of said first resistor;
• wherein said second wiring layer connects together one end in said longitudinal axial direction of said first resistor of one of adjacent resistance groups to the other end in said longitudinal axial direction of said first resistor of another of said adjacent resistance groups, and is also formed to extend over other resistors positioned between said first resistors of said adjacent resistance groups;
• and
• wherein said n driver circuits are connected each to one of said third resistors of said resistance groups and are also disposed at one side in said longitudinal axial direction.