Field effect transistor structure and manufacturing method thereof

An analog FET structure, comprising:

• a substrate of a first conductive type having a top surface;
• a shorter gate over the top surface;
• a source and a drain of a second conductive type in the substrate;
• and
• a shorter channel under the shorter gate,
• wherein a dopant concentration of a first conductive type comprises a single Gaussian peak measured less than 200 nm beneath the top surface, from one end of the shorter gate to the other end of the shorter gate along the shorter channel.

A method for manufacturing an FET structure, comprising:

• forming a gate on a top surface of a substrate of a first conductive type;
• performing a channel implant at a tilting angle approximately from 30 degrees to 45 degrees so as to form a dopant concentration profile of the first conductive type having at least a single Gaussian peak measured less than 200 nm beneath the top surface, from one end of the gate to the other end of the gate along a channel under the gate;
• forming a sidewall spacer of the gate;
• and
• performing a source and a drain implant.