Method for forming an integrated circuit with high voltage and low voltage devices

An integrated circuit having at least one first device operating at a first voltage and at least one second device operating at a second voltage higher than the first voltage, the integrated circuit comprising:

• a first gate structure and a second gate structure on a semiconductor substrate, the first and second gate structures being isolated from one another by at least one isolation structure;
• one or more first and second spacers on sidewalls of the first and second gate structures, respectively;
• one or more first double diffused regions adjacent to the first gate structure in the semiconductor substrate;
• one or more second double diffused regions adjacent to the second gate structure in the semiconductor substrate;
• one or more first source/drain regions formed within the first double diffused regions;
• and
• one or more second source/drain regions formed within the second double diffused regions, wherein a junction depth of the first and second double diffused regions is deeper by 0.2 to 0.5 μm than a junction depth of the first and second source/drain regions,
• wherein the first double diffused regions function as one or more lightly doped source/drain regions for the first device, and the second double diffused regions function as one or more lightly doped source/drain regions for the second device, and
• wherein the first source/drain region has an inner boundary line substantially aligning with an outer surface of the first spacer and the second source/drain region has an inner boundary line distant from an outer surface of the second spacer such that the hot carrier effect caused by the second voltage higher than the first voltage is reduced.

A method for integrally forming at least one first device operating at a first voltage and at least one second device operating at a second voltage higher than the first voltage, the method comprising:

• defining a first active area and a second active area on a semiconductor substrate;
• forming a first gate structure having a first gate dielectric layer and a first gate electrode on the semiconductor substrate in the first active area, and a second gate structure having a second gate dielectric layer and a second gate electrode on the semiconductor substrate in the second active area;
• forming one or more first double diffused regions adjacent to the first gate structure in the semiconductor substrate of the first active area, and one or more second double diffused regions adjacent to the second gate structure in the semiconductor substrate of the second active area;
• forming one or more first spacers on sidewalls of the first gate structure, and one or more second spacers on sidewalls of the second gate structure;
• and
• forming one or more first source/drain regions within the first double diffused regions and one or more second source/drain regions within the second double diffused regions, wherein a junction depth of the first and second double diffused regions is deeper by 0.2 to 0.5 μm than a junction depth of the first and second source/drain regions,
• wherein the first double diffused regions function as one or more lightly doped source/drain regions for the first device, and the second double diffused regions function as one or more lightly doped source/drain regions for the second device, and
• wherein the first source/drain region has an inner boundary line substantially aligning with an outer surface of the first spacer and the second source/drain region has an inner boundary line distant from an outer surface of the second spacer such that the hot carrier effect caused by the second voltage higher than the first voltage is reduced.