Hello, We want to choose a device for our design, and we are looking for the maximum voltage ratings (Vgs and Vds). In the readthedocs there is a section with electric specificactions but the voltage ratings are not explicit there. Are they somewhere else? Or should we consider the voltages used to measure saturation current as the maximum ratings? For example, Vgs_max of the HV LDNMOS would be 6V (attached image).

It seems that maximum VGS should be 6 V for those devices. There are also punch through specs, as shown in this image. Anyway, you should avoid stressing the transistors for better reliability. There are circuits for overvoltage protection, even if the required VDS is higher than VGS.

@Luis Henrique Rodovalho do you know the difference between Medium Voltage 5V and 6V devices? I see something about a V5_XTOR marking layer

The process is made for 3.3 V and 6 V devices. PVT corners are made for and error of 10%, so they consider 3.6 V and 6.6 V maximum ratings in corners. At least, I would use this corners for my simulations and it is what I saw for other process for this range. The truth is a bit more complex. Even those transistors rated for 3.3 V can work for long times if they are used with higher supply voltages. Some process even have some parameters available to calculate a probable IC lifespan with overvoltage. https://www.eesemi.com/oxidebreakdown.htm But I do get what you're looking for. SKY130 PDK has more specific info for their devices and maximum voltage drops across the transistor terminals.