Microsoft has made serious efforts to push the driver stack up to user space, since Windows Vista.

They use a theorem prover to validate drivers.

Static analysis is a enforced on the Windows source code via the Security Development Lifecycle Checks.

VC++ has quite a few security options that are enabled and used to compile the kernel.

After the whole Windows XP Swiss cheese episodes they ramped up quite a few security processes.

Windows 10 allows for individual application sandboxing.