An IC structure includes first and second transistors, an isolation region and a first gate extension. The first transistor includes a first gate and first source/drain regions respectively on opposite sides of the first gate. The second transistor includes a second gate and second source/drain regions respectively on opposite sides of the second gate. The isolation region is laterally between the first and second transistors. A first one of the first source/drain regions has a first source/drain extension protruding from a first boundary of the isolation region, and a first one of the second source/drain regions has a second source/drain extension protruding from a second boundary of the isolation region. The first gate extension extends from the first gate to a position overlapping the isolation region.