IE Problem on modal

Hello everyone, I have called this in my button onclick event. This works well on chrome for authenticated users, (not for anonymous) 

but in IE doesnt work, the error is 

 Unable to get property 'showModalDialog' of undefined or null reference

function addNewAdvertisementModal() {
  var u = _spPageContextInfo.webServerRelativeUrl;
  if (u.length > 0) { if (u[u.length - 1] != '/') u += '/'; }
  var options = {
 url: u + 'Lists/Advertisements/NewForm.aspx',
 title: 'AddNewAdvert',
 width: 640,
 height: 800
  }
  SP.SOD.executeFunc("SP.UI.Dialog.js", null,SP.UI.ModalDialog.showModalDialog(options));

}

note: I also tried

 ExecuteOrDelayUntilScriptLoaded(SP.UI.ModalDialog.showModalDialog(options), 'SP.UI.Dialog.js'); doesnt work.