a JD is simply a different type of degree, consisting of the requirement of 2 or 4 years of undergrad (depending upon the state requirements) and the 3 year (or 4 yr part time or whatever length of time required by the particular school) for the JD degree. Some say it is an undergrad degree, others say it is a graduate degree.
A Masters degree is traditionally considered as a 5 year degree, 4 years of undergrad and 1 year of graduate school. However, I notice that some online schools offer a two year master's degree without the undergrad requirements.
A PhD is generally considered as the next step up from the Masters, and to my knowledge, is the highest degree attainable at this time. It is the actual Doctorate's degree, whereas the Juris Doctor (Doctor of Jurisprudence) is not an actual Doctorate.
The Master of Laws, LLM, and LLD, Doctor of Laws (which is generally a foreign degree) and the JSD, the actual Doctorates, can be acquired only after the JD. However, some of the law schools now offer identical Masters of Law degrees available without the JD.
The LLB, Bachelor of Laws, is now generally a foreign degree, however there are a very few US Law schools which still offer the program. Interestingly, some of the SC Justices of recent years had only LLBs.