Surprisingly yes and it's actually got 114% coverage, Swiss law since 1963 has required

"Every inhabitant must have a protected place that can be reached quickly from his place of residence" and "apartment block owners are required to construct and fit out shelters in all new dwellings", according to articles 45 and 46 of the Swiss Federal Law on Civil Protection.

So every block of flats since 1965 has a nuclear fall out shelter in the basement usually with steel doors and a CBR (Chemical Biological and Radiological) ventilation system with air filters. Although it's common for the shelters to be used as storage areas by the flats tenants. The Swiss are also expert tunnellers and have created numerous fall out shelters carved into the mountains (along with Command and Control facilities and fortresses). As part of the "National Redoubt" or Réduit. Which has been around since the 1880s. Although many of the bunkers, hidden Observational Posts and gun emplacements have now been decommissioned.

Essentially the Swiss are surrounded by countries like Germany and France that go to war every few decades. Hitler had a plan to invade Switzerland during the Second World War Operation Tannenbaum (Fir Tree) which of course was never put into place. The Swiss with their limited man power and resources wanted to show to the Germans that any invasion would come at the cost of heavy casualties on the German side. Navigation within Switzerland would be slow and difficult as all the bridges and tunnels were mined and could be easily destroyed.

Post war the fear was that of a Soviet invasion or of fall out in the surrounding countries drifting into Switzerland in the 1960s the phrase "Neutrality is no guarantee against radioactivity" became popular. So again the policy was to make any Soviet invasion very costly in casualties and to protect its citizens.

Its also worth pointing out that Switzerland also requires all males to carry out two years conscription but the conscription is on a part time reservist basis similar to Britain's Territorial Army or America's National Guard. With the service regularly taking twenty year or more to complete. The reservists keep their weapon at home and once their time is up can buy their weapon for an administration fee.

Add on that Switzerland has a very challenging environment to fight in with lots of valleys, mountains and lakes, with very little in the way of natural resources and any attacker will pay a great cost with very limited rewards.

http://www.swissinfo.ch/eng/prepared-for-anything_bunkers-for-all/995134