MVC 3 Can't pass string as a View's model?

I have a strange problem with my model passed to the View

Controller

[Authorize]
public ActionResult Sth()
{
    return View("~/Views/Sth/Sth.cshtml", "abc");
}

View

@model string

@{
    ViewBag.Title = "lorem";
    Layout = "~/Views/Shared/Default.cshtml";
}

The error message

The view '~/Views/Sth/Sth.cshtml' or its master was not found or no view engine supports the searched locations. The following locations were searched:
~/Views/Sth/Sth.cshtml
~/Views/Sth/abc.master  //string model is threated as a possible Layout's name ?
~/Views/Shared/abc.master
~/Views/Sth/abc.cshtml
~/Views/Sth/abc.vbhtml
~/Views/Shared/abc.cshtml
~/Views/Shared/abc.vbhtml

Why can't I pass a simple string as a model ?