I found sometimes the label is printed with OptiMOS™ but sometimes it can not be found on the label,and this happens to many other part numbers, why is this?thx
I assume that you are talking about the marking on the component. Some part numbers are with the label OptiMos, some are not. As per the datasheet of IPD90P04P4, It is without OptiMos label on the part as shown below.
If you have seen this part with OptiMos label, Can you please share the image?