From time to time Microsoft in Redmond have positions open for software engineers specializing in compiler & tools development.
For those internal to Microsoft, I'd like to mention that a job is currently showing on the jobs site, with this description:
The F# team in Redmond is looking for a world-class developer to help us shape the future of F#! We are seeking a talented and highly motivated software engineer with experience in compilers, language tools and data-consumptive programming to help us ship the next version of F#. The ideal candidates would have a passion for the F# language, strong .NET programming skills, knowledge of data and cloud programming and experience working on compilers. An interest in F# evangelism is also a strong plus, as is experience in data-oriented work, object/relational mappings, web services and other connectivity technologies. An MS or PhD degree in Computer Science or a related technical field is considered an advantage.