Read multi level xml with null value if xml node not exists

My xml is something like this : <XMLDATA> <DETAILS> <PARAM1>1</PARAM1> <SPECS> <PARAM2>1</PARAM2> </SPECS> <SPECS> <PARAM2>2</PARAM2> </SPECS> </DETAILS> <DETAILS> <PARAM1>2</PARAM1> </DETAILS> <DETAILS> <PARAM1>3</PARAM1> </DETAILS> </XMLDATA>

I am looking for a table result like this :

  PARAM1         PARAM2 
 --------       -------- 
    1              1   
    1              2   
    2             NULL 
    3             NULL 

I try this :

 SELECT
       tab.col.value('PARAM[1]','INT')AS PARAM1,
       d.col.value('PARAM2[1]','INT') AS PARAM2
    FROM @PRODUCTS_XML.nodes('//DETAILS') tab(col)
    CROSS APPLY tab.col.nodes('SPECS') d(col)

But it just return the 1st row. Thanks.